


Bare Bones

by Kiar



Series: Undertale Beginnings [1]
Category: Undertale (Video Game)
Genre: Action, Angst with a Happy Ending, Anxiety, Backstory, Blood and Injury, Chapter 6 and Onwards Tags:, Death, Depression, Disintegration?, Feels, Fluff, Fluff and Angst, Implied/Referenced Torture, Kinda, Minor Violence, NO FONTCEST, No OCs, Origin Story, Probably some eventual angst, Prologue, Sorry Not Sorry, Spoilers, Swearing, That should go without saying, W. D. Gaster is not related to Skelebros, human skelebros, wow that's actually a tag
Language: English
Status: Completed
Published: 2017-04-01
Updated: 2017-07-06
Packaged: 2018-10-13 12:55:29
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings, Graphic Depictions Of Violence, Major Character Death
Chapters: 19
Words: 66,215
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10514196
Author URL: https://archiveofourown.org/users/Kiar/pseuds/Kiar
Summary: “look. i gave up trying to go back a long time ago… and getting to the surface doesn't really appeal anymore, either.”This is the story of how the Sans and Papyrus ended up in the Underground in the first place. The brothers are human... at first, anyway.Edit: As this fic has developed, it's come to be largely about Sans's (platonic) relationships with Papyrus and Gaster in the events leading up to the beginning of Undertale. Apart from some minor background characters in the first few chapters, there are no OCs. I hope you enjoy.This is my first real attempt at a fanfic, so please, I welcome any and all feedback!





	1. What's in a Name

**Author's Note:**

> This chapter is a bit short. A prologue to the prologue, if you will.

The brothers had straw-blond hair and sallow skin, but that was about where the resemblance ended. The eldest was short and clever while the youngest was tall and excitable. Despite their differences, however, they were fast friends.

  
The siblings lived in a mansion along with two dozen other caretakers, where they were paid for their services with food and shelter. Born and raised in the house, their world was by and large limited to the mansion’s grounds, and all its population composed of their fellow manservants and maids - along with the house’s family, of course. Their childhood was spent climbing trees, exploring the estate’s woods, and pranking the older inhabitants of the house. Though the youngest often spoke of the great adventures he would one day have, the two were rather content with the lives they had, and even after their mother passed they made no move to cut ties and strike out on their own. The people were kind and beds were warm. Those were the happy days.

  
The boys had once had average, dull names; ones that were so common as to be easily forgettable, and seemed to bleach meaning with each use. That all changed, however, one rainy afternoon somewhere in the middle of their childhood. Their mother, believing they were past old enough to have learned how to type (and herself having finished the yard work early due to the storm,) had set them down at a keyboard to teach them how to use a computer. The lesson hadn’t progress much further than a brief introduction to email and hapless pecking at the keyboard, but their mother had figured it was enough of a start for one day, and had left them to their own devices.

  
The Word document that had been left open immediately became experimental grounds for the two brothers. The first several minutes were spent filling the blank pages with random patterns of gibberish, and when they grew tired of that they moved on to toggling all the switches and buttons they could find at the top of the screen. Colors were an exciting discovery; the younger brother began to meticulously color every individual letter in order to produce a rainbow effect, but was quickly (and gently) moved aside by his older brother when it became apparent the patterning would likely go on for some time. The eldest was well aware of his younger sibling’s obsessiveness.

  
The older brother toyed with one of the options, and the text on the screen changed shape.

  
“Oh!” his little brother exclaimed. “What did you do?”

  
“I dunno,” he replied. “I just clicked something in this box.” He leaned in closer to the screen, squinting his eyes. Unlike his younger brother he knew how to read, but he wasn’t familiar with the word currently being displayed. He tried to sound it out. “Now it says… Cam...bri...a. Cambria.”

  
“Oh!” The younger sibling paused. “...What does that mean?”

  
His brother shrugged. “No idea.” He picked another option and the text changed again.

  
“Oooh,” his young brother admired. “Can I try?”

  
The older brother passed the mouse back over to his younger brother and sat back as he watched him flip through a series of fonts, sounding out the names when asked.

  
“Wowe!” the younger brother suddenly cried, causing his sibling to jump. “This one! This one is my favorite.”

  
His brother giggled at his reaction. “It _is_ pretty cool looking. This one is called…” He craned his head closer to get a look. “Pap… Papyrus.”

  
“Papyrus,” the younger brother repeated, trying out the word. “Okay!” he declared, clapping his hands before shoving the mouse back over to his brother. “Now it’s your turn!”

  
“My turn?”

  
“Yes! Now you have to pick a favorite.”

  
“Oh.” The older brother considered. “I think Papyrus is cool, too.”

  
His brother vigorously shook his head. “No! We can’t have the same favorite. You have to pick a different one.”

  
Unable to argue with this logic, the older sibling took the mouse back. He read the fonts silently to himself as he scrolled through the list.

  
“Heh. How about this one?”

  
His brother looked at the screen skeptically. “Why? That one looks… boring.”

  
“Well, I like the name,” he said. “Comic Sans.” It reminded him of the newspaper funnies he read each morning with breakfast. Though he originally had just liked them for the pictures, he was now starting to understand most of the jokes. He’d used to try explaining them to his brother as well, but he had rarely found them funny. Maybe he was just explaining them wrong.

  
“Just because of the name?” the younger brother questioned.

  
“Yep,” he said. “And it doesn’t look _that_ bad.”

  
“Well…” His brother didn’t seem convinced, but tried to show support. “I guess if you like it, that’s great!”

  
The older brother grinned, switching the font back to his sibling’s favorite.

  
“Not as great as Papyrus,” he said.

\---

The fonts became an inside joke between the brothers, codenames they used for each other when playing in the forest and sneaking about the estate on top secret missions. Slowly the codenames developed into nicknames, gradually wheedling their way into everyday use. The servants were quick to catch on to the brothers' new habit, and after that it wasn’t long before the names stuck.

  
Sans and Papyrus didn’t mind. They had, after all, picked out the names for themselves. And somehow, they just felt right.


	2. The Offer

**Summary for the Chapter:**

> A mysterious laboratory is being built in the mansion's backyard, leaving everyone to wonder what the Doctor might be cooking up inside.

**Notes for the Chapter:**

> I am not a humerus writer, so Sans is proving a bit of a challenge for me. Ah well, work outside your comfort zone, right?

The lab was only the Doctor’s most recent eccentricity. An observatory on the south plot still stood as testament to his last obsession, marking a period of nearly four years where he had buried himself in astronomy and astrophysical readings. It was largely abandoned now (as the Doctor tended to jump from one fascination to the next without the slightest warning,) but Sans and Papyrus had often visited to play and stargaze when they were younger.

The laboratory, however, was different. Seemingly overnight workers were brought in to assist with excavating a quarter acre of the property behind the mansion (much to the landscapers’ chagrin.) The facility sprouted from the ground in a matter of weeks, its steel skeleton only ever seen crawling with laborers like a colony of worker ants.

Not unexpectedly, the servants of the house could gossip of nothing else. Everyone had a theory as to what the structure was for, the most popular of which being that the lab was little more than a coping mechanism. In a scandal that had been all the house could talk about - until the laboratory, that is - two months prior the Doctor’s wife had taken their child and left the estate. Although fights between the sir and lady of the house had not been uncommon in the past, neither the Doctor’s wife or child had returned since. The theory that the Doctor was now burying his frustrations in yet another project seemed likely, though as to what that project entailed remained secret.

Often times Sans would stop in the middle of his work and just stand there, watching the edifice slowly take shape as he tried to puzzle together what it might mean. Usually Papyrus caught him in the middle of these daydreams and shooed him back to work, but Sans always found times to slip away and go back to watching. He found the mystery of it all exciting.

Then, one day, just as suddenly as the hired hands had arrived, they departed and left the monolithic structure in their wake. That same evening a hand-scrawled note appeared on the servant’s dining room table.

“What’s going on?” Sans asked at the sight of the small crowd that had formed in the dinette.

Papyrus squeezed in the room behind Sans, taking advantage of his height to peer over the group’s shoulders. “Looks like a letter.”

“Written by the Doctor,” one of the house’s maids turned back to explain. “Only one person whose handwriting is as bad as this.”

“What’s it say?” Sans asked.

“From what can be _made out_ ,” the maid said, smiling wryly, “it seems he’s looking for volunteers to work in the lab. Might have to work evenings and nights - there’s no set shifts, it seems.” She shook her head. “Honestly, I don’t know why he doesn’t just hire a few more hands for this. We’ll be short-staffed if too many make the switch. Although with the hours he’s proposing, I can’t imagine too many will.”

Papyrus was eyeing his brother, recognizing all too well the mischievous smile that had crept onto his face.

“You’re not seriously considering this?” Papyrus asked, raising an eyebrow at Sans. His brother laughed.

“Heh. Well, you know, I guess you could say I find the idea of working in a lab pretty _attractive_.”

Papyrus frowned at the comment, feeling he was missing something. Sans tried again.

“I’ve been meaning to _experiment_ with different career options,” he said. “This one seems like it’s got all the _elements_ I’m looking for.”

Papyrus sighed. “Really, Sans?”

“Well, might be too soon to say,” Sans replied, his grin widening. “I guess I’ll have to try it out to see if there’s any _chemistry_.”

Papyrus waved his hand before him, as if attempting to dissipate a foul smell. “You’re not going to take this job purely for the sake of making a few bad jokes, are you?”

Sans couldn’t suppress a chuckle. “Aw, come on, bro, what’s up with that _reaction_?”

Papyrus groaned and turned away, pressing through the crowd to head towards the kitchen. Sans trailed behind him.

“Don’t be so _negative_ ,” he continued, feeding off his brother’s annoyance. “This is exactly the sort of _catalyst_ we’ve been looking for.”

“Honestly, Sans,” Papyrus scoffed, finding the pot of stew that was sitting on the stove. Tonight there was no line, as most of the other servants were still gathered about the letter in the dining room. “Can’t you take anything seriously?”

“I am serious,” Sans said, dropping the puns for his brother’s sake. “I think it sounds interesting. We should do it.”

Papyrus spooned out two bowls of the soup and passed one to his brother. They settled against one of the counter-tops, unwilling to venture back into the crowd.

“Why?” Papyrus asked, taking a spoonful of the goulash as he regarded his brother. “Don’t you like what you do now?”

Sans shrugged. “Honestly, it can get a little boring. The yard work’s easy and working in the library can be fun, but… sometimes I just want a little more stimulation, you know?”

“I suppose,” Papyrus said, trying to understand his brother’s point of view. Truth be told, Papyrus quite liked what he did. Perhaps, given the opportunity, he’d want to work in the kitchen more often, but on the whole he was happy.

Sans took a bite of the stew and casually twirled his spoon around in the air. “I dunno, bro. Maybe I’m just looking for a little more… adventure.”

Papyrus paused. “Adventure?”

“Sure,” Sans said, reeling in the bait. “Who knows what the Doctor might be cooking up in there. Discovering cures to diseases, creating artificial intelligence, designing a spaceship-” A spark of interest flickered in his brother’s eyes at the suggestions. “Aren’t you the least bit curious?”

“Well,” Papyrus hesitated, “I admit I may be a _little_ curious. You don’t really think he’s trying anything that ambitious?”

Sans’s smile grew. “Only one way to find out.”

Papyrus slowly nodded. “When you do find out, I expect you will tell me all about it.”

“Aw, come on,” Sans said. He could tell his brother was almost on board with the idea and only needed another small nudge to finally cave. In fact he was a little surprised Papyrus hadn’t jumped at the idea at the first mention of ‘adventure.’ “You know it won’t be half as fun without you there, bro. Besides,” he added. “It will be a _noble_ endeavor.”

Papyrus frowned at Sans. “Was that a pun?”

Sans grinned. “Maybe.”

Papyrus couldn’t help but give a weary smile. “Well, alright. I’ll give it a try. But only if you lay off the bad jokes for a while!”

“You drive a hard bargain,” Sans said. “But I think I could give you a break _periodically_.”

Sans laughed as Papyrus scoffed in feigned disgust, but secretly Sans was overcome with equal amounts of excitement and relief. The brothers had grown up reading from the great volumes of the Doctor’s library, and after years of immersing himself in other worlds filled with fantasy beings and science-fiction creations, Sans could finally let loose some of that pent up imagination. He didn’t know what the Doctor would be working on, but he was more than ready to delve into whatever topic it may be. Sans hadn’t realized it until that moment, but this was exactly what he had been waiting for his whole life. A chance to try something new. A chance to work his mind more than his body. He wasn’t sure the Doctor would let him help directly with whatever he was doing, but he had to try. He wouldn’t waste this opportunity.

Though he couldn’t have fathomed it at the time, it would come to be a decision he’d regret for the rest of his life.


	3. The Laboratory

**Summary for the Chapter:**

> Sans and Papyrus start their fist day of work for the Doctor, and catch a glimpse of the inside of the lab.

The Doctor was a bit of a recluse. Though the house’s workers were inevitably aware of his presence - he tried picking up a different instrument every other month, it seemed, and when he wasn’t causing a cacophony with exotic instruments he was often making noise with power drills and other machinery - it was also seldom that the Doctor left his quarters. Food was delivered to and retrieved from his room at precise hours, sometimes with the trays taken away untouched. When he wasn’t making a ruckus he was likely engrossed in his (equally eclectic) studies, marked by the volumes of books that were ordered up to his room. All together, Sans and Papyrus maybe only saw the Doctor a few times a year, and had likely seen him on less than two dozen occasions over the course of their lives. It was with some fanfare, then, that he announced he would be moving to the newly constructed laboratory.

“Ahm, yes, excuse me,” the lean man said, edging his way to the top of the staircase. “Hello, yes, you,” he added as a maid on the lower landing did a double take.

“Sir?” she asked, shifting the basket of linens to her hip. A couple other passing servants had also stopped to stare, Sans among them. The Doctor appeared as if he had just gotten up from a nap - or perhaps he simply hadn’t bathed that day. His hair was flat on one side and wild on the other, his collared shirt half untucked, and his glasses hooked onto the front of his shirt. These he removed as he fidgeted, placing them on his nose after taking a moment to rub at his eyes.

“I need my assistants,” he said. “Our work starts immediately.”

“Assistants?” the maid echoed, not sure which of his dozens of staff members he was referring to.

“Yes, you know,” the Doctor said, waving his hands animatedly. “My assistants. The ones that will help with my research. The ones… hm… I have a list…” Distractedly, he began to pat down his pockets, hoping to discover it on him. Before he could get very far, however, Sans shuffled through to the front of the group.

“Oh! Hey, um, that’s me,” he said, causing the Doctor to look up. Sans had to refrain from taking the stairs two at a time. “I’m one of the volunteers.”

The Doctor looked at him with some doubt. “Ah, I see. Hm, well. I was hoping for someone… bigger. Perhaps we should wait for the others.” He waved the maid on and the crowd quickly dispersed, running off to spread the word.

Sans deflated somewhat, forcing down a small spike of frustration. His height was something he was still coming to terms with, but it was pretty clear by now that all his growth spurts were in the past. “Heh. Even if it’s a _tall_ order, no task’s too big for me. I can handle it.”

The Doctor hummed to himself, then turned back to the door that led to his quarters. “Possibly I’m wrong. But I find it likely your stature will be a problem.”

“I told ya, doc,” Sans said, following him into his room. “It won’t be a…”

Sans trailed off as he took in the state of the Doctor’s room. He hadn’t know what he’d been expecting the Doctor’s lounge to look like, but it certainly wasn’t this.

Stacks of paper buried the room’s furniture almost beyond recognition. The walls were impossible to make out behind the towers of packed items and discarded tools. And there were dozens - no, hundreds, - of large boxes overflowing with textbooks and manila folders. Probably thousands of pounds of paper. Sans nudged the closest box with his foot, which stubbornly refused to budge.

“...problem,” he finished weakly.

 

\---

 

Papyrus ended up doing most of the heavy lifting. The other three volunteers had also helped move the Doctor’s materials, though by midday only Papyrus had enough steam to keep going. Sans honestly didn’t know where he got all the energy. It certainly didn’t run in the family. On the bright side, Sans reasoned, he’d lasted longer than the Doctor, who’d bowed out after only four trips to the laboratory. His smugness dissipated somewhat when he remembered they were only a little over halfway through the stacks of literature.

“Resting already?” Papyrus teased, finding his brother draped over a chair in the Doctor’s lounge.

“It’s been _five hours_ ,” Sans moaned from his seat.

“Tara’s brought lunch out to the lab,” Papyrus said, ignoring his brother’s complaint as he picked up another box of textbooks. “The others are taking a break. But it looks like you already got the message.”

“It’s such a long walk,” Sans sighed. “There’ll be nothing left by the time I get there.”

“Well you certainly won’t get anything to eat if you stay here.” Papyrus paused in the door. “Coming?”

Sans mumbled something inaudible and pushed himself to his feet with a groan. “I don’t know how you do it, Paps. You’re like a perpetual energy machine.”

“I’m going to take that as a compliment,” Papyrus smirked, still waiting for his brother to catch up. Shifting the box of literature to his right side, he made a show of checking his watch. “Hm, I wonder if we’ll miss the tour.”

“Tour?” Sans asked.

“Yes, tour of the lab. The Doctor said-” but Sans was already out the door.

“Oh my, what a sudden burst of energy you have!” Papyrus laughed, following his brother down the stairs.

“I see through, you, bro! I see through you,” Sans huffed, navigating the mansion's hallways to head out the back. “I swear, if we get there and you made that up there will be puns to pay.”

Papyrus easily caught up with his brother, covering two of Sans’s strides with one of his own.

“You wound me, brother,” Papyrus shook his head. “But there really _will_ be a tour; it’s why I came to get you. Well, for that and lunch.”

Sans was breathing harder than he would have liked by the time they crossed the lawn and made it to the laboratory’s front doors. The others were gathered inside the entrance, a sort of lobby area that was currently furnished with the boxes that had been moved from the Doctor’s rooms. A folding table had been set up among the clutter and a small array of snacks and iced lemonade had been placed on its surface. The Doctor was riffling through one of the boxes while the other three volunteers were resting and eating nearby. It didn’t seem Sans and Papyrus had missed much.

“Thanks for the drinks, Tara,” Sans said, heading over to the table and grabbing a cup of lemonade. “That was really _ice_ of ya.”

Tara snorted. “Just trying to make sure you guys don’t get heat stroke. Doing all this work out in the sun at the peak of summer just isn’t healthy.” She gave the Doctor’s back a pointed look.

“We should be done by the end of the day,” Papyrus said, depositing his box with the others. “At least we’ll be out of the weather when we unpack all this.”

“Yeah,” Sans gave Tara a wink. “Don’t _sweat it_.”

“Ah, here we are,” the Doctor spoke up, pulling a book out of one of the boxes. He dusted off the cover, staring at it for a moment, then turned back to his assistants. The group straightened at his sudden attention.

“There will be required reading for this position,” the Doctor said. “We will be working with very sensitive equipment, and I can’t afford for any of you to be uneducated in the relevant topics.” The Doctor passed the book to Tara (apparently forgetting she was just there to deliver lunch) who in turn passed it to Papyrus. Papyrus frowned at the cover, giving his brother a worried look before handing it to Sans.

“I admit the subject matter is quite extensive,” the Doctor went on, “but this book should at least provide a decent foundation before you move on to more thorough literature.”

The title of the book was _Applications of General Relativistic Phenomena_ , and upon flipping through the pages Sans found the text to be packed full of complex equations and unfamiliar symbols.

“You gotta be kidding me, doc,” Sans said, passing the book along. “You want all of us to read this?”

“Hm, you’re right,” the Doctor considered. “I will order more copies so you will not have to share. That should expedite the process.”

Bewildered, Sans looked to his brother.

“Er, sir,” Papyrus tried. “I believe what my brother is trying to say is that… the material seems a bit… _dense_ , given our level of education. Perhaps assistants with degrees in some field of mathematics would be better suited for this task.”

“Oh, no, don’t be ridiculous,” the Doctor said, shaking his head dismissively. “It’s all very basic, I’m sure you will catch on in no time.”

“Sir,” Papyrus tried again, only to be interrupted.

“And enough with the formalities,” the Doctor grumbled, fiddling with a button on his sleeve in agitation. “Sir this - sir that - we’ll be working with each other every day from now on, and I’ve never been able to stand such impersonal titles for long. I’d much prefer to simply be called Gaster,” he said, surveying his rather surprised assistants. “Or Doctor Gaster, if you must.”

It was the first any of them had heard about Gaster’s dislike for formal titles - and seeing the Doctor frustrated was also a rare occurrence. The servants shifted awkwardly, not knowing what to say.

Papyrus, loath to uncomfortable silences, was quick to reply. “Er, yes sir. Doctor. Doctor Gaster.”

Gaster stared at Papyrus for a moment before throwing his hands in the air with a defeated sigh. Spinning around, he began to push through the maze of boxes and make for the back wall. “Alright. Let’s get on with it, then.”

His assistants scrambled after him.

“On with what?” Sans asked, snagging a hot dog from the lunch table before squeezing through the snaking path of clutter to the room’s back. There a set of double doors marked the exit to the lounge and entrance into the rest of the laboratory, which Gaster was in the process of unlocking.

“On with the tour, of course,” Gaster said, pocketing the key as he pushed the doors inwards. A breeze accompanied the action, the cool wind blowing outwards from the lab’s positive pressure. Sans and Papyrus shivered as they stepped inside.

“This,” Gaster said with a sweeping gesture as the others filed in, “is the main sector. Most of our time will be spent working here.” Gaster began to move on to lead the group to the next area of interest, before coming to a halt as he realized he was not being followed. His assistants were still standing just inside the doorway, their heads craned upwards. Gaster, too, gave another glance towards the monolithic machine suspended from the ceiling, briefly wondering what it would be like to witness it for the first time.

The room was two stories tall and almost the full length and width of the laboratory itself. It seemed the majority of the building was taken up by this single room, and the majority of the room taken up by a single, massive piece of equipment.

The machine was roughly toroid in shape and suspended by thick cables that stretched up into the rafters. Coils of exposed wires wound in and out of the machine like a network of veins, and a semicircle of computer consoles lay beneath the structure, giving its hollow center a wide berth. Servers and loudly whirring fans lined the walls, leaving little room to maneuver between the clusters of equipment skirting the machine’s shadow. Though the facility was brightly lit (and windows in the circular behemoth itself were giving off a dull, purple light,) the room felt strangely grave, as if an unseen force was weighing down on the laboratory and its inhabitants.

Sans took a breath, inhaling the sharp scent of metal and ozone. “Doc,” he said unable to peel his eyes away. “What _is_ all this?”

“This,” Gaster said, his mouth twitching into a smile, “is a time machine.”

**Notes for the Chapter:**

> What a shock! The Doctor is Gaster? Who could have possibly foreseen this unexpected turn of events?!
> 
> If the brothers' personalities seem a little different from their Undertale counterparts, that's intentional. They're at a different stage in life, after all, so changes are to be expected.  
> I'm trying to keep Sans close to his original character. Maybe he's a little less lazy and a little more motivated than his in-game self, but there's reason for that.  
> Papyrus is probably the most different. I'm trying to make him feel a little more grounded (and believable) while still maintaining the core aspects of his personality - namely, his outgoing nature and compassion. 
> 
> I'm curious to hear what you readers think about this portrayal. I know it's a bit of a divergence from other fics.


	4. The Machine

**Summary for the Chapter:**

> Sans and Papyrus tour the lab. 
> 
> Science and puns. Thanks for reading!

“Technically,” Gaster said, unable to keep from correcting himself, “a spacetime machine. But I find that to be rather less theatric, don’t you?” 

There was more stunned silence. Sans and Papyrus found themselves unable to look away. It couldn’t be true, but…  _ what if? _ Gaster spoke with such assuredness that, standing beneath such a leviathan, it almost seemed possible. Simply entertaining such thoughts brought back memories of their childhood, days when the line between wishing and believing was blurred. There had been a time when time-travel didn’t seem impossible, and for just a moment the brothers relived it. 

Marcus, one of the assistants, was the first to break the spell. “Doctor Gaster, this machine is amazing, but… surely…” he trailed off, looking helplessly to his fellows. 

“Time machines don’t exist,” Sans said, reluctantly grounding himself. “That’s just… science fiction.”

“It doesn’t exist  _ yet _ ,” Gaster corrected him. “But that’s why you all are here. Now come along, I’ve much to show you all before we can get started.”

Still somewhat stunned, the assistants followed Gaster around the room. 

“The electrical and cooling systems are below ground, accessible through by stair or elevator,” Gaster explained, pointing to the areas of interest. “All of the computer stations are located out here, in the main sector, however there are a few small labs - pertaining to chemicals and optics, mainly, - along the south wall.” Gaster led them through a doorway into a smaller chamber, flicking on the lights. An array of lathes, jigsaws, 3D printers, and other mechanical tools were scattered about the room. “This is the machine shop should we need to fabricate any specialty parts,” Gaster continued. “The time machine, as it is now, is just a skeleton of what it will become. The structure is there, however there are more delicate pieces we will need to assemble in-house. Raw materials can be ordered if what we have in storage,” he gestured to a lattice of drawers along the back wall, “does not suffice. I recommend that each of you read through the machine shop’s training manual I have put together and avoid severing any limbs. Moving on...”

Gaster grew more animated as he talked, making wild gesticulations the more enthused he became in a subject. His previous irritation quickly evaporated as he spoke of his work, and the doctor became more confident and boisterous the more he delved into the physics behind his creation, (completely oblivious to the glazed-over eyes of his assistants.) By the end of the tour they had been up catwalks and down into the basement; woven in and out of tightly compact labs, and shuffled carefully past glass refrigerators full of dubious liquids. Sans felt like he was walking through a mad-scientist’s lab - and maybe he was. 

The tour ended where they’d began, standing beneath the looming torus. Gaster gave his assistants a piercing, unreadable look, then clasped his hands behind his back and walked to the center of mechanical ring. 

“Here,” he said, “is where history will be made. This is the spot where we will rip a hole in spacetime and force physics to bend to our will. There is much work to be done and much more for you all to learn. Today we will continue to move my documentation to the lab - tomorrow we will set about unpacking and then begin to divide up tasks based on your appropriate skills. In one week,” he said, holding up a matching finger, “we will begin the first stage of calibration. In that time I expect you all to have read  _ Phenomena  _ and have a decent grasp of the fundamental theories behind the work we will be doing.” 

Having been uncharacteristically quiet while on the tour, Sans now spoke up. 

“Look, doc, this sounds like a great thing you’ve got going on here. And I certainly don’t want to  _ dampen your momentum _ , heh… But we can’t just become quantum physicists overnight.” He grinned weakly, falling back on his puns out of nervousness. “That’s just not something you can  _ force _ .” 

Gaster stared at Sans for a moment, decidedly unamused. “What was your name again?”

“Uh, it’s Sans,” he said, his smile pulling tighter. Sans knew the Doctor didn’t get out of his room much, but they  _ had  _ met several times in the past. Was he serious? 

“Sans,” Gaster repeated. “Well as I see it, if you don’t think you’re up to the challenge then I’ll find someone else who is.” Before Sans had a chance to react, the Doctor flicked his hand at the group and turned his back to them. “That is all for now. You may return to your work.”

Sans stood there until Papyrus gently shook his shoulder, startling him out of his silent fuming. Catching his brother’s eye Papyrus simply shook his head, then led them both out of the room. 

\---

“ _ Not up to the challenge _ ,” Sans growled, throwing himself on his bed later that evening. “Who does he think he is, threatening us like that? We  _ volunteered  _ to help.” 

“I hardly think that counts as a threat,” Papyrus said, sitting down on his own bed on the other side of the room. Papyrus stretched his arms and rolled his neck with a content sigh.

“And what was that about not knowing my name?” Sans continued, ignoring his brother. “We’ve only been living here for  _ nineteen years _ .” 

“Seventeen for some of us,” Papyrus quipped. “Perhaps he is just bad with names.”

Sans gave his brother a skeptical look. “Why are you defending him?”

“Because you’re overreacting,” Papyrus said, leaning down to stretch his legs out next. “You just don’t like that he challenged you.” 

Sans bristled, opening his mouth to retort, then stopped. Letting out an airy laugh instead, Sans rolled over to look at his brother. “Heh, you’re right. Guess he got under my skin. How do you do that, Paps?”

“It’s called a cool down,” Papyrus said, pivoting to stretch his back. “Helps alleviate some of the soreness after a workout.”

“Not that,” Sans chuckled. “Although that does sound pretty  _ cool _ . I mean, how do you stay so level headed? Nothing gets to you.”

Papyrus shrugged. “I’m sure the Doctor meant well. He’s just a bit…” he hesitated, searching for the right words. 

“Crazy?” Sans supplied.

“I was going to say ‘enthusiastic.’” Papyrus got up and went over to their wardrobe, pulling out his night clothes. “Anyway, if it doesn’t work out, then we can always go back to our normal duties.”

“Do you want to?” Sans asked. 

“Honestly?” Papyrus brought over a set of nightwear to Sans as well, knowing he’d likely just sleep in his work clothes otherwise. “I… want to believe the Doctor when he says it will work. I want it to be real.”

Sans laughed, taking the clothes from his brother. “Yeah… me too. He seemed so sure of everything when he was talking about it. He has part of me thinking he’s crazy, and another part of me convinced he can really do it. Hah, guess that makes me crazy, too, doesn’t it?”

“Maybe not crazy,” Papyrus considered. “Just… inspired.”

“That sounds like code for crazy,” Sans teased. 

“Then that makes two of us,” Papyrus said, sitting down with a smile. “A time machine. It really would be the ultimate adventure, wouldn’t it?”

“Yeah,” Sans grinned. “Where would you go? Or when?”

Papyrus considered. “Medieval times. Somewhere with knights.”

Sans chuckled. “I should have guessed. You’d make a good knight; you’re athletic and chivalrous enough. But for me,” Sans shook his head. “It’d be a  _ knightmare _ .” 

After a moment of silence, Papyrus raised an eyebrow. “Really?”

“Aw, come on, it’s  _ joust  _ a little pun.”

Papyrus massaged the bridge of his nose. “If we’re doing this again I’m going to bed.” 

“Right now?” Sans laughed. “I bet you’re not even re- _ moat- _ ly tired.” 

Papyrus grabbed his clothes and made for the bathroom. “I regret saying anything.” 

“Wait, wait, I don’t want to  _ drag-on _ , but the next one will  _ slay  _ you.” The door shut with a definitive  _ clack _ , leaving Sans chuckling to himself. 

Laying back on his bed, his grin slowly faded to a soft smile as his thoughts roamed elsewhere. It had been an interesting day to say the least. Mysterious labs, time machines, and mad scientists. No wonder Papyrus wasn’t ready to back out, it was just like the make-believe games they’d acted-out as kids. Only this… this might be real.

Sans glanced over to  _ Applications of General Relativistic Phenomena _ , which was sitting on his bedside table. The other assistants had seemed all too eager to let Sans take the book when he offered to read through it first. Probably they were counting on him not finishing it by the end of the week so they would have an excuse not to read it. He couldn’t blame them really; he’d only grabbed it in a burst of defiance after Gaster’s challenge, which he was now beginning to regret. Even so, some of his earlier stubbornness rekindled at the thought, and after a few minutes of mulling it over he pushed himself off the bed and took the textbook over to his desk. Sans flicked on the table-lamp and turned off the room’s main lights, then settled into his chair as he flipped to the first page. The small light wouldn’t keep Papyrus up, he knew, and despite all the exercise Sans wasn’t quite yet tired enough to go to bed. His mind was too full of thoughts to rest now; maybe the book’s dense lessons would help him drift off. 

Sans didn’t notice when Papyrus returned from the washroom, and was still reading when his brother fell asleep. 

**Notes for the Chapter:**

> I know, I'm wordy, but I promise shit's going to hit the fan here in about two chapters.


	5. Challenge Accepted

**Summary for the Chapter:**

> Sans doesn't get much sleep. Papyrus worries. Gaster is oblivious.

Papyrus woke up to his internal clock, finding it brighter than he was used to. Had he overslept? That would be unusual. Papyrus pushed his covers aside and reached for his wristwatch, pausing as he noticed the light in the corner of the room. 

“Sans!” Payprus exclaimed, causing his brother to jump. “Did you wake up before me?”

“Uh,” Sans coughed, clearing his throat. His voice sounded gravley. “Wake up?”

“Oh my god.” Papyrus sat up. “Did you even go to bed?”

“Oh,” Sans yawned, stretching in his seat. “I guess not. What time is it?”

“Nearly six,” Papyrus said. Then, thinking it might be necessary to clarify, he added, “In the morning.” 

“Whoops,” Sans chuckled, though it came out more like a growl. “I guess I lost track of  _ time _ . This book really  _ pulled me in _ .” Sans laughed, as if he’d said something funny. 

“You need to get some rest,” Papyrus said, getting up and heading over to Sans’s desk. “Your puns aren’t even making sense! That is concerning.” 

“Gravity, Papyrus,” Sans chuckled. “‘Pulled me in.’ Because-” he yawned. “-because it’s about gravity.”

“That doesn’t even - good lord,” Papyrus stopped himself as he caught sight of Sans’s desk. Dozens of handwritten notes covered the surface, partially obscuring the textbook that sat open to a page near the back. “You’re almost done with it?”

“Nah,” Sans said, suppressing another yawn. “Finished it already. Second pass was to take notes. Maybe finish that in another hour or two. Pretty interesting, actually.” Sans rubbed at his eyes. 

“If you say so.” Papyrus frowned at his brother in concern. “You really should get some rest, though. You won’t be able to work in the lab like this. I’ll tell Gaster-”

“No!” Sans bolted upright. “No way, bro, I can’t miss today. I’ll be fine, I promise. I’ll just grab a cup of coffee and, heh,  _ grind  _ through the day.”

Papyrus didn’t seem convinced, but there was little he could do to stop him.

\---

Sans was on his fourth cup by the time he slogged in the lab’s front doors. He had brought  _ Phenomena  _ with him, intending to return it or pass it on to whomever would take it next. Sans looked around the room, unsurprised to find he was the last to arrive.

“You look terrible,” Gaster commented, glancing at Sans as he shuffled into the lab. 

“You, too,” Sans said, sipping his his coffee. Gaster’s head snapped back to Sans as one of the assistants quietly gasped. 

“Sans,” Papyrus admonished, but his brother shrugged it off.

“Didn’t sleep much, either, huh?” he asked.

Sans observation hadn’t been an exaggeration. The Doctor looked even more disheveled than he had the day before, though he’d thrown a lab coat over his work clothes (in an attempt, Sans guessed, to disguise the fact that he hadn’t changed.) 

To everyone’s surprise, however, the Doctor just smirked and shook his head. “I suppose that’s an accurate assessment. Speaking of…” Gaster took a stack of papers and began passing out pages to each of his assistants. “This is a list of tasks you will be performing and areas of expertise you are expected to learn. I have attempted to tailor the tasks to your apparent skillsets.”

The Doctor continued to explain his methodology for his tasking, but his assistants had stopped paying attention. Papyrus read through his own print out; apparently he would be helping in the machine shop, which was better than he had been expecting, truth be told. After the tour yesterday he’d been worried he’d have to work with chemicals or handle something equally fragile, but hardware was something he knew he could work with. Leaning over his brother’s shoulder to read what he’d been assigned, Papyrus abruptly stiffened. 

_ Sans: _ the paper read.  _ Maintenance and custodial duties.  _

Papyrus slowly looked down at his brother, bracing himself for his reaction. To his surprise, however, his brother was smiling. Somehow, that did little to alleviate Papyrus’s unease. 

\---

That first day Sans helped the others unpack and organize Gaster’s literature. When he’d come across a book that seemed particularly worn he’d pause, making a mental note of the title before placing it carefully on its respective shelf and moving on to the next one. By the end of the day he had made a decent list, and was ready to put his plan into motion. The fact that he had fallen asleep twice before noon, however, meant that things would have to wait. That night he collapsed onto his bed before dinner and didn’t wake up until the next morning.

The next day he took three textbooks from Gaster’s library and began to read. Papyrus warned him he’d be in trouble if he got caught, but Sans just waved him off.

“Just doing what the doc ordered. Can’t complain about me not cleaning if there’s nothin’ to clean yet, right?”

Papyrus didn’t like this logic, but saw the futility in trying to get his brother to do something more productive. When he set his mind to something, he could be as stubborn as Papyrus. Maybe more.

As his brother had predicted, Sans did get caught. Gaster seemed more annoyed by Sans’s choice of literature than the fact he wasn’t working, however.

“You’re wasting your time,” Gaster sniffed. “Those books won’t make much sense without having read  _ Applications of General Relativistic Phenomena _ first.” 

“Oh, yeah,” Sans stretched lazily. “I finished that one already. Guess I couldn’t help  _ myshelf _ .” 

Gaster’s haughtiness turned into surprise with a blink of his eyes. “You read it all yesterday?”

“More like the night before,” Sans said, his tired smile suddenly causing Gaster to recall the assistant’s fatigue from the previous day. 

“I see,” Gaster said, taking a second look at the stack of books next to Sans. The Doctor considered the texts, then tapped one on the spine. “Best start with this one. What’s your mathematics level at?”

“Only up through calculus,” Sans admitted. “But I’m a quick read.” 

“There’s a book on differential equations in my office,” Gaster said. “You should read that one, too.” 

“Oh,” Sans said, his smile faltering. “Uh, okay. Thanks?”

Gaster walked away without another word, leaving Sans in a state of vague confusion. If Sans had been expecting Gaster to be provoked - or impressed - he was sadly mistaken.

On the third day since the laboratory was opened Sans showed up late (despite his brother’s attempts to rouse him) and with more coffee. That day was spent in alternating intervals between napping and reading. At one point Marcus had nervously woke him to inform Sans there had been a spill in the chemical lab, and Sans waved him off, promising he’d get to it later. He didn’t.

On the fourth day Sans claimed one of the storage rooms as his own. He moved his scattered notes and small stack of books into the makeshift office, creating a desk out of discarded boxes from Gaster’s move. It proved to be a good place to read - and sleep - discretely. 

By the fifth day Papyrus was worried. He wasn’t sure Sans was sleeping at night anymore, and he hadn’t seen his brother eat or drink anything other than coffee in at least two days. 

“You need to slow down,” Papyrus was telling Sans that evening. “What you’re doing isn’t healthy.” He set a plate down on one of the boxes next to Sans. His brother eyed it skeptically. 

“Roast?”

“You need to eat,” Papyrus said, producing a bottle of ketchup next. Sans’s eyes lit up, squirting a healthy serving of the condiment onto his plate.

“You must be pretty worried if you’re serving ketchup with pot roast,” Sans said, digging in. “Usually you try to hide it.”

“It’s an insult to the roast,” Papyrus folded his arms.

“It’s delicious,” Sans disagreed. 

Papyrus sat down with his brother. “What are you trying to accomplish, Sans? I don’t understand why you are doing this.” 

Sans swallowed a mouthful of the roast. “I’m just studying, bro. The doc said he wanted us to learn the material, right? What’s the big deal?”

“You’re not eating or sleeping - much,” he added, before Sans could latch onto the technicality. “You seem a little… obsessive.” 

Sans snorted. “Obsessive?” He glanced around the room at the thought, noting the growing stacks of papers and textbooks. Before long he’d have a collection to rival Gaster’s. “I’m not obsessed, just… trying to prove a point.”

“That’s what I’m worried about,” Papyrus said.

Sans tossed his fork down on the empty plate and leaned back in his chair, avoiding his brother’s gaze. “Don’t be worried. I’m fine.”

“No, you’re not,” Papyrus sighed. “Just… just slow down a bit is all I’m asking. Get some sleep tonight. Please?”

“Aw, Paps,” Sans moaned. “That’s cheap. You know I can’t say no when you’re like this.”

“Promise me?” Papyrus pleaded. “Sleep and food - not coffee, that doesn’t count.”

“The coffee, too?” Sans lamented. Papyrus just looked at him with pleading eyes. Sans caved. “Alright, alright, I promise to do better. Get some sleep and eat some real food. How’s that?”

“And talk to Gaster,” Papyrus added, causing Sans to groan. “Just talk to him!” Papyrus insisted. “Stop being so… indirect. If you want him to take you seriously, just say so.”

“You know I’m not good with that kind of stuff,” Sans said. 

“Yes, you’d much rather be passive-aggressive,” Papyrus huffed. “At least try? For me.”

Sans rubbed the back of his neck, then gave a slow nod. “I’ll try. That’s the best I can give ya.” 

“Thank you, Sans,” Papyrus said, sweeping his brother up into a quick hug. Sans laughed, captive in his brother’s arms. 

“Alright, enough hugs. This is getting un _ bear _ able.”

His brother practically dropped him. 

\---

Day six started much the same as the others, though Sans  _ had  _ made an effort to get up at a more reasonable hour. He found his brother already in the machine shop (still fastidiously working through Gaster’s manuals in an effort to avoid the likelihood of severed limbs) and the other assistants off trying to learn their new tasks as well. Gaster was at one of the computer terminals in the main sector, hunched over a monitor with intense focus. 

Sans considered locking himself in his closet for the rest of the day to keep reading, but he had told his brother he would at least  _ try  _ to talk to Gaster. Best to get it over with now.

Hesitantly, Sans approached the station Gaster was working at. The Doctor didn’t notice his approach, too buried in his own work to be bothered. Sans’s gaze wandered as he tried to find the words for what he would say, though these half formed thoughts quickly fell away as he caught sight of the Doctor’s screen. 

“Is that C?” Sans asked. Gaster gave a start, swiveling around in his chair to face his assistant. 

“C++,” Gaster said. “You code?”

Sans considered talking his skills up, but quickly dismissed the thought as bragging would only dig himself a hole he’d likely fall into later. 

“Not much,” he admitted. “Just took some intro classes online, and messed around with JavaScript a couple years ago when Paps wanted to make a website.”

“Hm,” Gaster said, an unreadable expression on his face. “Can you read this?” He pushed his chair out of the way, making room for Sans at the desk. Sans frowned at the screen, wishing he’d brushed up on his programming skills before he’d opened his mouth. 

“Uh, a bit,” Sans said. “Something to do with random number generation?”

Gaster gave a curt nod. “That’s the meat of it, anyway. Was there something you wanted, Sans?”

“Oh,” Sans grimaced, remembering why he was there. “Yeah, uh… nevermind. It’s nothing. Was just gunna… return your books.” He had tried anyway, and that’s all he’d promised his brother. 

“I see,” Gaster said. “In that case, you know where the texts belong. Let me know if you need any other references.”

“Oh, sure,” Sans said, edging away. “Thanks, doc.” 

Well, at least it could have gone worse. Truth be told the last of the frustration that had fuelled his initial defiance had pretty much been dispelled by the talk with Papyrus. Gaster could sometimes come off as arrogant, but the truth was that he was more distracted than anything. Besides that, he was letting Sans read through all his research; Sans couldn’t stay mad at him for long. 

One week to the day they had started moving Gaster’s belongings into the lab, the scientist assembled his assistants to evaluate their progress. 

“It has come to my attention that only one of you has finished reading  _ Applications of General Relativistic Phenomena _ ,” Gaster began. “This is very disappointing. I expected more.” The assistants had not forgotten Gaster’s initial threat about replacing any volunteers that did not meet the Doctor’s expectations - it seemed, however, Gaster had. 

“I expect you all to catch up soon,” the Doctor continued, “for I have additional materials I will need you all to read in the coming weeks.” A couple of the assistants let out quiet groans. “Calibration efforts begin today, and as such roles will need to be somewhat shifted. Marcus,” he said, causing the assistant to snap to attention, “I will need you to dust off the spectrometers and ensure they are functioning properly. Alice, you are to assist Papyrus in the machine shop with the lense fabrication process. Sans, I will need you to review some code models I am working on. Isabella, you may continue your work with the optics. Any questions?” After an array of blank (and even overwhelmed) looks, Gaster dismissed them. Sans followed the Doctor back to his work station. 

“Uh, so what do you want me to look at?” Sans asked as Gaster took a seat. Gaster gestured to the computer terminal to his right, and Sans sat down as well. 

“I will send you the relevant scripts and you will check them to make sure they are functioning properly,” Gaster said. “You will likely have to independently derive some of the equations that are being used to ensure no mistakes were made on the backend. From there, if you seem to be handling it well, you will help me write future models. Does that sound reasonable?”

Sans blinked. “Yeah… yeah! That sounds great, actually. So, will I be working here, or…?”

“Of course,” Gaster said. “Working close at hand seems most efficient if you have any questions. Besides,” Gaster waved a hand. “That storage closet of yours is no place to be doing science.

Sans felt his ears get hot. “Oh, heh heh… you know about that…” Sans cleared his throat, turning to his computer as he turned it on. “You know, doc, I think I misjudged you.”

Gaster hummed to himself and tapped at the keyboard as he began to work. “Funny thing, Sans. I believe I can say the same for you.” 

**Notes for the Chapter:**

> Ketchup with pot roast really is delicious though, I don't care what you guys say. 
> 
> This chapter marks the end of the story's backstory/buildup. I've been looking forward to writing the next chapter; things should be faster paced from here on out.


	6. Activation

**Summary for the Chapter:**

> A time skip of a few months.

Days turned into weeks, and those turned into months. Under Gaster’s tutelage Sans’s learnings flourished, and it wasn’t long before the scientist took the young man as his apprentice. The other assistants struggled to keep with the lab’s fast pace, and though the machine’s development continued to run into a succession of roadblocks, it seemed there was always some new experiment to run or specialty part to manufacture. 

“I’m telling you, bro, it really isn’t that bad,” Sans said, waving his spoon at Papyrus over breakfast. Papyrus watched the gesticulation, noting it as a habit his brother had picked up from Gaster. 

“You’re not going to be able to convince me that quantum entanglement is just like a crossword puzzle, Sans.” Papyrus took a bite of his toast and shook his head. “Crossword puzzles are easy.” 

“But it is just like your puzzles!” Sans exclaimed. “Each piece you stitch together is a part of something else. You can’t put in a word that doesn’t fit, and you can’t overwrite letters that are already in place. See? They’re both a system of equations, the trick is just solving all the blanks.” 

Papyrus grimaced. “You make crossword puzzles sound like work.” 

Sans chuckled. “It does take work, it’s just fun so you don’t notice it. Like with physics.”

“I’m going to have to disagree,” Papyrus said, massaging a temple. Sans’s smile faded. 

“Hey, Paps… I’ve been meaning to ask… do you not like working in the lab?” Sans stirred his bowl of cereal. “I mean, I knew you weren’t totally convinced at the start, but… if you don’t like it you don’t have to stick it out for me, you know?”

“Oh! No, no I  _ do  _ enjoy it,” Papyrus said, frustrated with himself for making Sans worry. “I like working in the shop. Manual labor is something I’m good at - and making things is fun! It’s just all the math that can be overwhelming,” he added. “You know I’m not very good at math.” 

“Hey, that’s okay,” Sans said, backtracking slightly on his attempts to get Papyrus as engaged in the science as he was. “When it comes to physical stuff you got be beat several times over. Heh, if you averaged the two of us I’d bet you’d have an normal person.”

“Average is boring,” Papyrus teased. “We could combine both of our strengths instead and become super-average! Above-average?” He paused. “Hmm, my language fails me...” 

“Great?” Sans suggested. 

Papyrus laughed. “Well, if you insist.” 

Before Sans had a chance to respond a crack of thunder shook the house, causing the lights the flicker and the chandelier to gently tinkle. The brothers glanced up towards the ceiling, where the telltale hush of rain signalled a seasonal downpour had just begun.

“Days like these I wished the lab wasn’t all the way across the field,” Sans remarked. Papyrus stood up and took their plates to the sink. 

“We should leave now before the lawn floods,” he said.

“I hate to  _ rain on your parade _ ,” Sans grinned, “but it might be too late for that.”

“Please Sans, this day doesn’t need to be any worse than it has to be,” Papyrus scowled.

“Aw, sorry, bro,” Sans said, clearly unsorry. “I didn’t mean to  _ dampen your spirits _ .” 

“I’m getting the umbrellas,” Papyrus said, ignoring his brother.

“Come on, don’t be such a  _ wet blanket _ ,” Sans snickered, following after. 

“I will leave you behind,” Papyrus warned, pulling an umbrella off the rack. “And you will have to hike through the rain all on your own.” 

“But two’s company, Papyrus,” Sans said. Papyrus hesitating, watching his brother closely. “...and  _ three is a clou _ -”

Papyrus snapped the umbrella open and stormed off into the rain. 

\--

“Have you thought about trying to use the lightning?” Sans asked Gaster as they climbed down the stairs to check on the generators in the basement. “The solar panels aren’t much use on days like these.”

“I’ve considered it,” Gaster admitted. “An array of lightning rods across the estate could be constructed and linked to the grid - however controlling such a high surge of current might prove troublesome. And the storms themselves are unpredictable.”

Sans went over to the nearest generator to check its power levels. The charge seemed to be holding well, but they were still slow to fill. “Well, looks like we could use all the power we could get,” Sans said, noting the metrics in his notebook. “If your calculations are right then we’re going to need a better power source for this thing to be sustainable. Geothermal?”

“Not the right geography, I’m afraid. And before you even ask,” Gaster added, “I am already looking into nuclear. It seems the most energy efficient option - however the paperwork for trying to create your own nuclear reactor is a nightmare. I believe the government now has me on several watch lists.” 

“I have to admit,” Sans chuckled, “I’m not surprised you’d meet such  _ resistance _ .” 

Gaster snorted. “I admit I didn’t think they had the  _ capacity  _ for such rigorous supervision.” 

“Oooh, nice one.” 

“Thank you.” 

“But you know,” Sans said, finishing his notes and heading back to the stairs to wait for Gaster, “I think looking into alternate sources of power will be worth your time. The results could be quite  _ electrifying _ .”

Gaster shook his head with a chuckle. “That one was too easy, I expect better from you, Sans.”

“You mean I need to be less  _ direct _ ?” he said, raising an eyebrow. Gaster couldn’t help but crack a grin. 

“ _ Currently _ , I think you could use some  _ alternate  _ sources of inspiration.”

The two were laughing by the time they reached the top of the stairs. 

“Are you encouraging him again?” Papyrus demanded, catching the tail end of Sans and Gaster’s conversation. “He really doesn’t need the encouragement.” 

“At least  _ someone  _ acknowledges my comedic genius,” Sans said. 

“I find it to be more like torture,” Papyrus said. 

“It’s only ever extremes with you two, isn’t it?” Gaster observed, heading over to his computer to enter the metrics they’d taken into the simulation. “Genius or torture, delicious or disgusting, hyperactive or napping.”

“Not always,” Papyrus said, leaning down to pick up a box of fresh supplies. The raw materials had been delivered earlier that day and were currently deposited in the middle of the room, where most miscellaneous items wound up until they found a more permanent home. Gaster had said they’d need to clear the space out before testing would begin, but that was still months away. 

Papyrus carried some sheets of metal back into the machine shop as he spoke. “There is  _ one  _ thing we can agree on.”

Sans nodded, leaning against a server as he fixed Gaster with a rare, serious look. “Tomatoes.”

“Tomatoes,” Gaster repeated flatly. 

“Pure ambrosia,” Sans said.

“Food of the gods!” Papyrus called from the back room. 

Gaster blinked. “I don’t understand.”

“Ketchup,” Sans began ticking off on his finger. “Pizza.”

“Bruschetta!” Papyrus called.

“Ketchup.”

“Tomato soup!” 

“Ketchup.”

“Spaghetti sauce!” Papyrus returned from the shop to pick up the next load of supplies. “Speaking of spaghetti, dinner should be ready soon. Would you like me to go grab some servings for you both as well?”

“Oh no, that’s quite unnecessary,” Gaster said, waving Papyrus off. 

“Yeah, bro, don’t worry about it,” Sans said. “‘Sides, it would be all soggy by the time you brought it back.” Sans noticed Papyrus’s disappointed look before continuing. “And anyway, I wouldn’t miss pasta night for the world.” 

“Really?” Papyrus said, his eyes lighting up. “You almost never make it to dinner on time.”

“Yeah,” Sans scratched the back of his head. “I should probably be better about that. Anyway, tonight seems like a good night to call it early, what with this weather. You coming, too, Gaster?”

“Me?” The Doctor looked surprised. “I’ve never had dinner with the staff. It wouldn’t be awkward?”

“Maybe a little,” Sans admitted with a chuckle. “So what do you say?”

Gaster never had the chance to answer. 

A sudden crack of lightning split the air, shaking the laboratory and bursting several lightbulbs in a succession of brief flashes of light. The group dove for cover as shards of glass rained down on them, attempting to shield their faces. Discharge jumped from the outlets as all the computer terminals blipped off - the persistent whir of the cooling system in the basement shuddered to a halt. Before the quiet had much time to linger, however, a new sound took its place.

A tremble passed through the facility, building into a soul-shaking hum. The resonation grew so low and intense that Sans could feel the vibrations in his chest - he ground his teeth against the sensation, pressing his hands to his ears. 

“What is it?” Sans shouted to Gaster, hoping the Doctor knew what was going on. Gaster, however, was looking up, and when Sans followed his gaze he saw Papyrus was doing the same. 

The machine was buzzing with electricity. Purple light began to shine from within the toroid’s windows, quickly becoming blindingly bright and bathing the laboratory in an intense shade of violet. A metallic whine rose with the machine’s awakening, punctuated by snaps of electricity as sparks arched from the torus. The air smelled suddenly and sharply of ozone, and all the hair on Sans’s arms stood on end. 

He should have recognized it at once, but he was still too much in awe to believe what was happening. Perhaps if he’d been faster he could have done something. Maybe if he’d been more vigilant, he’d have realized where Papyrus was standing. For years he’d think: what if, what if...

The building charge was let loose in a concussion of light. Electricity exploded from the machine, funneling downwards from its center and engulfing Papyrus in a shroud of lightning. Papyrus screamed, and so did Sans, frantically scrambling to his feet as his brother was caught in the machine’s hold. 

“Papyrus!” he cried, making a blind lunge towards the machine even as something caught his ankle and sent him sprawling to the ground. Sans kicked at it, too distressed to look away from his brother’s veiled form. “Papyrus!” he yelled, still trying to disentangle himself. “Papyrus, no!”

“Sans, stop!” Gaster shouted, pulling back on his assistant’s leg. “It’s too dangerous!”

Sans looked back, realizing what had stopped him. “Let go!” he struggled desperately, kicking at Gaster with his free leg. “Let go of me! Papyrus - I have to stop - no, no, no!” 

“You can’t stop it!” Gaster cried. “You’ll just get pulled in as well!” 

“Papyrus!” Sans screamed, still trying to escape the Doctor’s grasp. He could barely see his brother through the blinding haze - in fact, the scene had lit him up like an x-ray machine, and for a moment all Sans could see was his skeleton - but he could still hear his agonized screams. “Please!” Sans begged, not even sure who he was pleading to. “Please, no, please, stop, Papyrus-”

And then it did stop. The vortex of electricity gave one more turn before collapsing in on itself and extinguishing in a burst of light. Sans was temporarily blinded by the display, leaving him only with the sensation of Gaster’s hand around his leg and an intense ringing in his ears. Static rippled between the floor and the metal on his clothes, but he didn’t feel any of it. When his hearing returned he realized he was still babbling, repeating his brother’s name over and over again. The pressure on his ankle vanished, and Sans pushed himself up to his knees, groping the floor in front of him. Which way was it exactly? Even if he couldn’t see he could find his way to the machine’s center - he would drag his brother out if he had to. He would - 

A light flicked on somewhere to Sans’s left and his head jerked in that direction, wondering how he’d gotten turned around. 

“It’s over, Sans.” Gaster’s voice wavered as he spoke, and he set the flashlight down on the table with two violently shaking hands. “I- I’m so sorry.” 

Sans stared, trying to understand. It was Gaster. Gaster had the light. Then he wasn’t blind after all; the laboratory was just dark. 

Not only dark, but quiet and empty as well. As Sans looked back into the shadows of the lab, he could see that the space beneath the machine was clear. All the boxes of equipment that had been sitting there had vanished. The floor was spotless. 

And Papyrus was gone.

**Notes for the Chapter:**

> Here we go.
> 
> Next chapter will be up sometime Friday night, hopefully.


	7. Gone

**Summary for the Chapter:**

> In my plot skeleton (hah) the only thing I had listed for this chapter was "lots of emotions."
> 
> Actually I'd planned for this chapter to only be a short scene at the beginning of a larger chapter before it got out of hand. I'm not terribly pleased with the pacing, admittedly, but it was so emotionally exhausting to write that I think I'm just going to have to post it as-is. 
> 
> Er, enjoy?

Sans was still sitting on the floor when the front door of the lab burst open. “Doctor Gaster!” Isabella called, trying the room’s light switch and finding it inoperable. “Is everything alright? We saw the lights from the house.”

“Oh, oh dear,” Gaster said, shaken from his shock. “I- I really don’t know how to say this.” His gaze flickered to Sans, who hadn’t so much as flinched at Isabella’s entrance. “There was an accident. Papyrus was…”

“He’s fine,” Sans said, stirring. “Papyrus is fine. He’s just- just- we’ll get him back, okay?” Sans stood up, brushing past Gaster as he went over to a computer terminal. He pressed the power button and waited for it to turn on.

“Sans,” Gaster said quietly.

“The logs might have captured the power surge,” Sans continued. “And we just took recordings of the generator levels. Between the two we should be able to analyze the anomaly and recreate the event.” Sans pushed the power button again, but the computer still didn’t turn on. Sans grumbled, giving the terminal a kick.

“Sans,” Gaster meekly tried again. “It’s probably fried.”

“I’ll get it working,” Sans insisted, grabbing the flashlight off the desk and pulling out the unresponsive computer.

“What’s going on?” Isabella asked. Sans ignored her.

“We should head back to the house,” Gaster said. “I… we all need to process what’s happened.”

“There was a screwdriver around here somewhere,” Sans muttered, pulling open several drawers. “Ah, here.”

“Is it just you two?” Isabella asked, the worry in her voice growing as Sans and Gaster dodged her questions. “Wasn’t Papyrus out here, too?”

Gaster flinched as the screwdriver clattered to floor with a metallic clang. There was a moment of silence, then Sans bent to pick it up. Wordlessly, he began to unscrew the back of the computer’s casing.

“He’s,” Gaster started, his voice beginning to tremble once more. “Papyrus is… he’s gone-”

“HE’S NOT GONE!”

Sans’s frame was shaking, his knuckles white where he clenched the desktop. “He’s not! He’s just - just somewhere else, and I’m going to bring him back, and it’s- it’s going - it’s to be okay-” Sans choked, struggling to draw in a breath. “He’s- he’s fine- Papyrus-”

“Oh, dear.” Gaster rushed to Sans’s side, resting a hand on his back. “Breathe, Sans. Deep breaths.”

“I-” Sans gasped, tears welling up in his eyes. “I can’t-” He grabbed one of Gaster’s sleeves as he tried to steady himself. His breaths were coming fast and shallow - the more he tried to control his breathing, the more he realized he couldn’t, and the faster the panic set in.

“It’s okay, it’s okay,” Gaster said, trying to support his assistant.

“It’s not!” Sans sobbed, the tears breaking free as he verged on hyperventilation. “It’s- it’s not okay- I- I didn’t- I didn’t-”

“Hush,” Gaster said, shakily lowering Sans to the ground as his legs gave out. “Don’t talk, just try to breathe, okay?”

Sans didn’t reply, overcome by sobs and violent shudders.

“I’m going to go get help,” Isabella said, hurrying out of the lab.

Sans found his face buried in Gaster’s coat, his tears soaked up by the heavy material. His chest felt like it was in a vice, and his head was spinning from the lack of air, but he couldn’t make himself stop.

“He- he’s my little brother,” Sans forced out between gasps. “I’m- I’m supposed to - supposed to protect him. That’s- that’s what big brothers are s-supposed to do. And now he’s- he’s-” Sans felt the world tip at the thought.

“I’m so sorry, Sans,” Gaster repeated. “I’m so sorry. I don’t know what to say. I never know what to say to people. I’m not… not good at this.”

In any other situation Sans might have laughed - he wasn’t exactly a people-person himself - but Sans was hardly listening to anything Gaster was saying.

“Why- why’d you stop me?” he suddenly asked, looking up at the scientist. His breathing was still erratic, but he forced himself to stumble over the involuntary sobs. “Why?”

“I couldn’t let you get caught in it, too,” Gaster said, looking away from Sans’s anguished face. “I couldn’t lose you both.”

“He’s not lost,” Sans choked, his grip tightening on Gaster’s labcoat. “I coulda d-done something. I coulda - coulda stopped it somehow. You sh-shouldn’t have stopped me.”

“You know you couldn’t have done anything,” Gaster sighed. “There was nothing-”

“You didn’t even give me the chance!” Sans cried, roughly shoving Gaster away as he raised a fist. Gaster leaned back, raising a hand of his own in alarm. “I sh-should have had the chance! Instead I- I had to just _watch_ and- and- and I just _hate being so f-fucking helpless!_ ” Sans slammed his fist into the ground, sending a stab of pain up his arm.

Gaster remained quiet as Sans sobbed, his knuckles pressed against the lab’s hard floor. His hand throbbed and it dimly occurred to him he might have done some damage, but the pain gave him something else to focus on. He latched onto the sensation, using it to fuel his frustration.

Sans couldn’t have said how long he sat like that, but gradually his breaths began to come easier and his sobbing subsided. The anger slowly ebbed, replaced by a heavy weariness that was physical as much as it was mental. Even after he had stopped crying, neither he nor Gaster stirred until the lab’s door opened.

“I brought Marcus and Alice,” Isabella said, rushing over to Gaster as he stood to meet her. They had brought more lights with them, which they turned on the two scientists. Sans flinched as one flashed in his eyes, and he heard the ghost-cries of his brother. “What can we do? Is anyone hurt?”

“I brought a medical kit,” Marcus added, kneeling down beside Sans. “Bell said there was an accident. Are you hurt?”

Sans shook his head.

“Your hand is bleeding,” Marcus noticed. Sans looked down, slowly uncurling his throbbing hand to see that Marcus was right. His knuckles were skinned.

“It’s nothing,” Sans croaked. His throat felt tight and raw.

“I’ll patch it up.”

“No,” Sans said, withdrawing his hand before Marcus could help. “It’s nothing.”

Isabella and Alice had stepped aside with Gaster and were talking in hushed tones. Despite their attempt to be discrete, however, the lab was quiet and their voices carried.

“... what do you mean ‘gone?’” Sans could hear Alice whisper.

“At least let me sanitize it,” Marcus said, raising his voice. Sans looked past Marcus, watching the group talk. “No sense letting it get infected.”

“...should we call the police?”

“No!” Gaster and Sans said at the same time. Gaster gave a start, realizing Sans had been listening. Marcus moved out of the way, abandoning his attempt to distract the young scientist.

“Are you sure?” Alice asked. “If… if he’s missing…”

“Involving the police would complicate things,” Gaster said.

“They’d shut us down,” Sans added, his voice still hoarse.

Isabella shifted uncomfortably. “Would that be a bad thing?” The assistants nervously glanced towards the machine while Sans and Gaster looked away.

“I think,” Gaster said, “that may be a conversation for later. For now we should go back to the house. Try to… to collect our bearings. In the morning we can talk, but for now…”

The assistants nodded their compliance, but no one moved. Eventually Marcus held out a hand to Sans.

“Can you stand?”

Sans lifted his hand, then dropped it. “Yeah. I… I can walk. But… I want to talk to the doc, first.” Sans sniffed. “In private, please.”

The assistant looked to Gaster, who waved them on. “It’s fine. We’ll be right behind you.”

“Are you sure?” Alice asked. Marcus stood up and joined the others by the door.

“Yes,” Gaster said, though he didn’t sound sure. “We just… need a minute.”

The assistants lingered for a moment longer, but saw there was nothing they could do. They left reluctantly and quietly, Alice handing Gaster another flashlight as they departed.

Once they were alone, Gaster let out a heavy sigh and went over to the nearest work station, falling into one of its chairs. He set his head in his hands.

“Sans,” Gaster started, but Sans cut him off.

“I’m sorry,” Sans said, watching his fingers moved as he flexed his injured hand. “I shouldn’t have yelled at you. It wasn’t your fault. I know you were just-” his breath hitched, and he had to take a moment to keep himself grounded. “I know you were just trying to protect me.” Like he hadn’t been able to do for his brother.

“It _is_ my fault,” Gaster said, shaking his head. “This lab wouldn’t exist if not for me. I am responsible for what happened here tonight. And I understand if you resent me for it.”

Sans sat back with a sigh, and wiped at his eyes against his sleeve. His shirt was just as soaked and did little to clean his tear-stained face, but it made him feel like a little bit less of a mess. Finally he looked over at the Doctor, his expression empty and tired. “I don’t blame you, doc.”

Gaster looked up with a grimace. “I’d rather it be me than you.”

Sans blinked at the comment, then let out a breath of air that almost could have been a laugh. “I guess you _do_ know me.”

“Don’t think like that,” Gaster said. “Please. Promise me you won’t blame yourself for this.”

Sans slowly shook his head. “I… I don’t know if I can.” Sans shuddered in another breath, forcing back a wave of despair that threatened to overcome him once more. No - no he couldn’t let himself think about it right now, not after he’d just managed to calm down.

“Look, doc,” Sans croaked, and he stopped to clear his voice. “I- I just wanted you to know that I don’t put any of this on you. You… you’re my friend, and this was an accident. So I don’t - I _couldn’t_ \- hate you for this. I needed to say that.” Sans passed a hand over his face. “But.. I also really don’t think I can keep talking about all this right now.”

“Oh- of course,” Gaster stammered. “I think, probably, it would be best if we - you - tried to get some rest.”

Sans gave a weary nod. He didn’t think his mind was ready to sleep, but he felt exhausted. It was the strangest sensation: alert, yet drained. Overwhelmed, yet hollow. A detached part of himself tried to understand how these dichotomies were possible.

“Sleep,” Sans repeated dumbly. “Yeah. Guess I should try.”

“Good.” Gaster sounded relieved. “Do you need help? Here.” Gaster stood, reaching out to help Sans up. This time, Sans took the offered hand. The assistant found his legs were shaky, but capable of supporting his weight.

“Thanks, Gaster,” Sans said, simply standing there for a moment. His gaze wandered around the room, inexorably drawn towards the machine’s center. In that open space, burned into his retinas, Sans could still see the afterimage of light and his brother’s silhouette. It was with great difficulty that he looked away.

When Sans realized Gaster was still waiting for him, he took a breath, opened his mouth, and faltered, only then realizing he had nothing to say.

“...Are you ready?” Gaster asked, noticing Sans’s hesitation. “I’ll help you back to the house.”

Slowly, Sans shook his head. “I want to walk back on my own.”

“Oh,” Gaster said, clearly unsure about leaving Sans alone. “I don’t know...”

“Please, doc. I… I need some space.” Sans looked up at Gaster. “I’ll be okay.”

The conflict and unease was clear on Gaster’s face, but when Sans refused to look away, Gaster caved. “Alright,” the Doctor reluctantly agreed. “Just… I don’t like the idea of you being… here… by yourself. Please come back to the house soon.” He frowned, adding, “I’ll send Alice to come get you if you don’t.”

“Just be a few minutes,” Sans wearily agreed.

Gaster patted Sans on the shoulder, looking as if he had more he wanted to say. When Sans didn’t respond, however, the Doctor let him go and left without another word. The gentle hush of rain accompanied Gaster’s leave, and the lab smelled briefly and sweetly of mist. Then the door closed, the laboratory became silent once more, and the scent drifted away.

Sans kept his eyes to the floor as he turned around and walked back over to the machine. He stood there for a moment, staring at the ground and feeling the weight of the machine overhead. He tried to imagine, and found he couldn’t. He spoke his brother’s name aloud, but there was no one to respond. He waited, but nobody came.

Then, carefully, Sans turned his thoughts inwards. There was a knot of emotions there, wound so tight they were nearly ready to snap. He picked through them, one at a time, as he gently unraveled the mess.

Fear was the most prominent. He was afraid for his brother. Afraid he was hurt. Afraid he was unreachable. Afraid of his own inability to help. And most of all, afraid that there really was no way to get him back.

But this fear could not help him. It could only paralyze his actions and cloud his mind - he needed his mind now more than ever, so Sans set his fear aside.

There was anger, too. Frustration with himself and, yes, even with Gaster. He was angry that they hadn’t been more careful. Angry at their own audacity. Angry with himself that he had failed as an older brother. But this anger was equally unproductive, and it would only lead to reckless behavior. Sans couldn’t afford that now.

There were other emotions as well - sorrow, guilt, shame, regret. But beneath all of those was something else. Something smoldering. It was resolved, and passionate, and decisive. It was an emotion that, given the opportunity, could push all other emotions to the side. It was exactly what Sans needed.

Sans took this one and fed it. He had to use it if he was going to try to get his brother back - no, he _was_ going to get his brother back. He didn’t care how long it would take, or how hard he’d have to work for it. There was no alternative. He would accept nothing less. He would do anything - _literally anything_ \- to save Papyrus.

Sans was filled with determination.


	8. Determination

**Summary for the Chapter:**

> Sans and Gaster resume work on the machine.

Gaster was relieved to hear Sans had returned to his room the night before. Alice had scolded him when she found out he had left Sans alone, but the assistant had come back in his own time and further drama was averted. That wasn’t to say rumors weren’t spreading, however; the servants were avoiding Gaster like the plague, and conversations fell silent the moment he stepped into a room. 

Gaster would need to figure out what to tell them all soon. Papyrus had been a favorite around the house, and while he had asked his lab assistants not to go to the police, that didn’t mean others wouldn’t. Did Papyrus and Sans even have family elsewhere? Gaster wasn’t sure, but it was something they would need to discuss. 

He wanted to give Sans some time to himself before they spoke, but by noon Gaster had become too restless to wait any longer. When Isabella stopped by to check on him, Gaster asked her to wake Sans and fetch Marcus and Alice as well. He paced his lounge nervously, still trying to put together what he would say. 

“Sir?” Isabella said, returning a few minutes later. “Sans isn’t in his room. Tara saw him in the kitchen this morning, but no one else has seen him since.” 

“What?” Gaster exclaimed. “Where else would he be?” 

Isabella didn’t need to answer. They both looked out the window and across the lawn, where the laboratory sat quietly waiting. 

Gaster swore, grabbing a jacket as he rushed out of the room. 

 

The lights were on in the laboratory when Gaster pushed open the doors. “Sans?” he called when he found the main sector empty. He hadn’t expected a reply, and was surprised to hear a distant, “Down here,” drift up from the basement. Gaster followed the echo, heading down the steps to the generators. 

Sans was nowhere to be seen, but some faint ratcheting could be heard from the back of the room. Gaster climbed around the heavy equipment, making his way to the lab’s cooling system. There he found Sans bent over one of the radiator inlets. Gaster’s heart sunk, recalling his assistant’s actions the night before. His first instinct had been to go back to work - to deny that anything had even happened. Had Sans relapsed? Gaster didn’t think he was capable of handling it again. 

When Sans turned around, however, there was something different about him. Dark shadows encircled his eyes, that was true, and he looked as if he hadn’t gotten much sleep. But there was an unfamiliar intensity to his gaze. Serious and focussed. 

“I was wondering when you’d come,” Sans said, setting his tools aside. “You were right about the computers. A lot of equipment fried last night.” 

“Oh,” Gaster said. “Yes… yes, I see.”

Sans stared at him when Gaster didn’t go on. Silence began to pool between them. 

“You think I’ve lost it,” Sans finally said, stuffing his hands in his pockets. “That I’m just doing this to cope.”

“N-no, of course not,” Gaster stammered, thrown by how easily Sans had guessed exactly what he had been thinking. “I’m- we’re all just worried about you. But you seem to be doing… well?”

“Honestly?” Sans said, scuffing a foot as he looked at the ground. “I’m really not. I’ve got… all sorts of feelings I’m not dealing with right now.” He paused for a moment, before suddenly fixing Gaster with another sharp look. There was a fire in his eyes, Gaster thought. “But that doesn’t mean I’m not fit to be here. In fact,  _ this  _ is what’s keeping me grounded. I want to fix it,” Sans said, turning to fetch a notepad before handing it over to Gaster. “And finish it. This is a list of all the pieces damaged by the lightning.”

Though Gaster had initially planned on getting Sans to come back to the house so they could discuss as a group what their options were moving forward, these thoughts were pushed aside by curiosity as he glanced through Sans’s notes.

“I think they can be replaced in a week or two,” Sans continued. “And the damage isn’t as bad as I first thought. The fuses protected the servers, so we’ve still got all the research, models, and simulation data. Given that… I think we’d be able to run a system’s test by the end of the month.” 

Gaster gave a start, looking up from the list. “One month? That’s far more aggressive than our schedule had planned for. Sans, rushing something like this-”

“I know how this sounds, but I’m not being reckless,” Sans insisted. “I’ve run the numbers, and I think we’re closer than we ever realized. And if I’m wrong,” Sans swallowed, his confidence wavering, “then- then I’ll stop. We’ll take a step back and figure out what to do about… about him being gone.” Sans’s gaze unfocused for a moment, and he inhaled a sudden, sharp intake of breath. Gaster braced himself for another meltdown, but instead Sans just shook his head, and when he looked up again his resolve had returned. 

“Please, Gaster,” Sans said. “Just give me this. Just give me the opportunity to  _ try _ .” 

It wasn’t healthy, Gaster knew, to let Sans put off dealing with Papyrus’s loss for another month. And yet he couldn’t bring himself to tell Sans no, either. He still believed his machine could work, and as long as that might come to be true there was the possibility that Sans was right. However unlikely, there was always still a chance that the machine’s actions could be undone - or prevented, for that matter. 

That, and he couldn’t help but recall what his assistant had said the night before.  _ Why did you stop me? _ Sans had sobbed.  _ You didn’t even give me the chance! _

Oh, the others were not going to like this. 

“Alright,” Gaster agreed, and a wave of relief passed over Sans’s face. “We’ll keep working.”

“Thank you, doc,” Sans said. “Thank you.”

\---

It was ready in less than a month. 

Sans had been right - after reviewing the servers they’d found a data dump that had taken place just as the event had begun. It cut out part way through when the fuses had blown, but all the initial conditions were documented. The recordings were a goldmine for their simulations. 

The most time consuming part was restoring the power reserves. A significant portion of the energy that had been consumed by the machine had derived from the lightning strike itself, and replicating that power draw was no easy feat. Sans checked the generators’ status every day, constantly on the lookout for other power sources and ways in which their storage and delivery system could be made more efficient. For Sans it was the most frustrating aspect of the project, for by and large the only solution was to simply wait for the batteries to fill. 

When he wasn’t analyzing their electrical system, Sans spent most of his time pouring over the models he and Gaster had developed for spacetime navigation. They had tried using the values generated by the lightning strike, but no matter how they turned the numbers their equations never quite added up. 

“It doesn’t make sense,” Sans sighed, pushing himself away from the computer. His chair swiveled as he rolled away, and he watched the ceiling spin. “We have to be missing something. The equations must be derived wrong. A missing variable.” 

“We’ve been over the derivations a hundred times,” Gaster said. “It’s more likely the data is at fault.”

“It can’t be, it’s direct readouts from the machine,” Sans said. “There’s just some piece we don’t understand.” 

“The math is clear cut,” Gaster disagreed. “We interpret with respect to the spatial data and output an infinite time. We interpret the temporal data and the solution gives us negative spatial coordinates. The place or time to which the portal opened cannot exist.”

“Well it had to lead  _ somewhere _ ,” Sans argued. “Or somewhen.” 

“Or the portal was unstable,” Gaster said. “Which would explain the nonsensical values we’re getting.” 

“It was stable,” Sans said. “It had to be.” 

Gaster decided not to push the point. “Regardless,” he said, “We’ll be using spacetime coordinates we understand for the dry run. Perhaps once we have a controlled dataset to compare to, the values will begin to make more sense.” Sans didn’t respond; Gaster couldn’t tell if he was silent out of disappointment or frustration. “At any rate,” he added, hoping to make Sans feel better, “we should have the answer to that mystery tonight.”

Sans sat bolt upright in his chair, his eyes as wide as saucers. “What? Tonight?”

“Well, yes,” Gaster said, frowning in confusion at Sans’s sudden panic. He’d thought his assistant would have been eager to hear his decision. “I believe everything is in order to beginning the test today.”

“But- but I thought it was going to be this weekend,” Sans said, glancing nervously at Gaster before looking away just as fast. “Maybe we should give it another day to be safe. Heh, after all, you said we shouldn’t rush this, right?” His mouth was pulled into a nervous smile, but he appeared more shaken than excited. 

Gaster’s frown deepened into suspicion. “What is this about, Sans? I thought you were impatient to get going on this.”

“Yeah, I am,” Sans said, fidgeting with his hands. “I just… I guess I just didn’t think it’d be  _ today _ . I… I really want it to work,” he added.

Gaster’s expression softened. “Ah, I see. If this is about our agreement - about taking a break if the test doesn’t work - I want you to know that I won’t hold you to that.” Sans looked up in surprise. “I know you only offered that so I would agree to let you keep working on the machine. But Sans, I wouldn’t have stopped you then, and I don’t intend to now. You have the brightest mind I have ever seen, and you are always welcome in my lab.” 

Sans was quiet for a moment, then he gave a soft chuckle and wiped at the corner of his eye. “Geez, doc,” Sans said, meeting Gaster’s look with a sad but authentic smile. “Getting all sappy on me like that. You’d give Papyrus a run for his money.” 

Gaster gave a start when he heard Sans speak his brother’s name. It was the first time he’d said it outloud since the night of the accident. He didn’t want to be overly optimistic, but perhaps his assistant was reaching a turning point.

“But… thanks,” Sans added. “It was nice to hear that.” 

“Of course,” Gaster said, still somewhat bewildered. “I’d thought most of that should have gone without saying. But as we’ve previously established, I am not an expert at expressing myself.”

Sans laughed, kicking his chair back over to the computer terminal. “You and me both, doc. Hey,” he added, sniffing the air. “Is that burgers I smell?”

“It is about lunch time,” Gaster noticed. “And I think we’ve done about all we can do in here. Would you like to take a break? We could use one before we start setting things up for tonight.”

“Sounds great,” Sans agreed, standing up with a stretch. “Oh, wait, actually, I wanted to kick off one last sim before I head over,” he said, glancing back at one of the terminals. “I just got an idea for another configuration we could try. Don’t worry, it should be done running before tonight’s test.”

Gaster shrugged. “It can’t hurt to try.”

“Save a burg for me?” Sans asked, already back to typing at the computer. “I should just be a minute or two.”

“If you take too long they’ll grow cold,” Gaster said in light-hearted warning. He made for the door, turning around in the entryway as he waited for a snappy comeback, but his assistant was already too absorbed in his work to notice. 

Gaster left him, smiling to himself. For the first time in what seemed like years, things were beginning to feel normal again. Perhaps Sans was just dealing with his brother’s loss in his own way. Things like these always took time, Gaster knew, but he was ready to have his old apprentice back. Those first few months, before the accident, had been some of the most enjoyable days of his life. He’d always assumed that normal relationships were something that would be beyond him, but maybe he was not so much of a lost caused as he’d supposed. 

The night of the accident Sans had not been completely coherent, but Gaster did clearly recall his apprentice calling him a friend. How many friends did Gaster have? He thought he could probably count them all on one hand. While he wasn’t sure how it was supposed to work with an employer and an employee, he valued his friendship with Sans. Gaster hadn’t ever vocalized this, he realized, and wondered if that was something he should do. After lunch, perhaps, he would express his thoughts. Or maybe over lunch. It occurred to him that this was probably something he should have emphasized before now, especially given Sans’s emotional state over the past few weeks. Well, it was too late for that, but he intended to make it right. 

Gaster was only halfway across the lawn when he heard the generators power up. 

He paused, thinking his ears must be playing a trick on him. There was no reason for the generators to be coming online. They were only to be used when… when…

Gaster turned back around, watching the lab as disquiet twisted in his gut. No, he refused to believe this was happening. Sans wouldn’t… would he? There were other explanations. Perhaps Gaster was really hearing the cooling system cycling on. He knew what that sounded like, but… but it was possible…

Lights flickered through the second-story window, and Gaster felt sick. Oh no.  _ Oh no. _

 

Gaster burst through the lab doors to find Sans standing at the center of the machine. His assistant smiled sadly when he saw the Doctor, hands tucked casually in his pockets. Overhead, the machine was beginning to glow.

“You shouldn’t be here, doc,” Sans said. “It’ll be going off any minute. I wouldn’t want you to get caught in it, too.” 

“Sans, what are you doing?” Gaster demanded, though his authoritative tone was undercut by the shaking in his voice. He was afraid - and upset. He knew exactly what Sans was doing.

“It was going to be at night,” Sans said. “When you all were asleep. I wanted to avoid, well,  _ this _ . But seein’ as you moved the test run up to tonight, I had to improvise.” 

“I don’t understand,” Gaster said, his eyes flicking over to the machine’s control station. Perhaps he could still stop this. “Why not wait until after the test? Until we know how to operate it properly? It’s not ready.” 

“It’d take another month for it to recharge,” Sans said. “And then of course you’d have some other test in mind. And then I’d have to wait another month. And then there’d be another test. And another.” Sans sighed. “I can’t keep waiting, Gaster. This thing might not be fully functional, but it can take me where it took Papyrus. And that’s the only place I want to go.” Both looked up as static began to crackle on the surface of the torus. 

Gaster crossed quickly to the machine’s terminal, his fingers flying over the keyboard to see what Sans had done.

“You can’t stop it,” Sans said, making no move to intercept Gaster. “I wrote my own code to automate the routine. Once it’s active, there’s no going back.” Despite his assumed aloofness, Sans flinched when an arch of electricity zapped the floor by his foot. 

“You don’t even know where he went,” Gaster pressed. Sans was right about the computer; there was nothing he could do to shut it down from here. Gaster turned away from the terminal as he decided to try a different tactic. He hadn’t brought it up before, but now was the time for hard truths. “Papyrus could have come out a thousand feet in the air - or a thousand feet beneath the Earth. There’s a good chance he’s already dead, and if that’s true then you’re about to join him.” 

“Yeah,” Sans said, surprising Gaster as his smile slipped. “I know. I guess I just hope that if I’m not right… then you are.” 

Gaster was speechless. Was he understanding Sans correctly? That he wouldn’t want to live without Papyrus? He knew Sans loved his brother, but this wasn’t right. It certainly wouldn’t be what Papyrus would want. For a genius, Gaster thought, Sans could be exceptionally stupid. 

Setting his jaw and ignoring the growing whine and crackle of the machine, Gaster marched over to Sans.

His apprentice took a surprised step back. “Whoa, whoa, doc, what are you doing?” Gaster could feel the energy growing overhead - the air was getting hot. “Get out of here! It’ll go off any second!” 

Gaster grabbed Sans’s wrist as his assistant recoiled. “We’re leaving. If you fight me,” he added as Sans tried to pull away, “then we’re both going through.”

Sans stared at Gaster in disbelief even as Gaster wondered what he was doing. The purple light overhead had become blindingly bright, and the snaps of electricity had reached an uproar. There were only moments left. 

Several conflicting emotions passed over Sans’s face. Fear, anger, desperation. Gaster was beginning to think he’d misjudged his apprentice when Sans suddenly swore, all the tension going out of him.

“Sh-shit!” Sans cried, yielding to Gaster’s pull. The moment Sans gave in Gaster bolted for the edge, his assistant half a step behind. The thrum of the machine could be felt in his skull - leads of electricity arched up from the floor to meet the bolts that sparked down. A violent vibration pulsed through the lab, and the apparatus hit its climax.

They were nearly at the edge of the torus when the machine discharged. The lab flashed white as Sans and Gaster became engulfed in a torrent of lighting. Energy tore through them, consuming their senses. Gaster couldn’t see or hear - he couldn’t even feel if he was still holding onto Sans. But the wave of excruciation that ripped through him next made all previous thoughts seem of little importance. 

With brief but sudden clarity, Gaster understood why Papyrus had screamed. 

**Notes for the Chapter:**

> Sans is fine with putting himself at risk for his brother, but endangering someone else is a different story. Gaster was betting on this... even though it took him too long to make the gamble. 
> 
> I won't be able to keep up my every-other-day posting routine. The next few weeks will be busy. But hopefully the next chapter will be up by the weekend?
> 
> Next Chapter: The Underground


	9. The Underground

**Summary for the Chapter:**

> Sans discovers the consequences of using the time machine.

Sans could feel himself being ripped apart. It seared through his body, boiling down through his skin and muscle and sinew until it reached his very bones. The heat ate him up, bleached his mind, turned everything he knew and felt into raw sensation. He was stretched - twisted - melting. Everything and nothing at once.

The passage of time became eluding. It could have been a moment or an hour. Sans was beyond comprehension - all he wanted was for the pain to end.

Yet the heat grew more extreme. The force that had burned inwards now pushed out, expanding from Sans’s core at an excruciatingly slow rate. It was like something was pressing back, fighting to contain the energy that threatened to explode from him. He wanted to let it go, let it all be released so he could lapse back into blissful darkness - and for a moment his will seemed to bolster the expansive force, causing the warmth to grow a fractionable degree more tolerable. But like a dying star, the initial wave of energy could not overcome his gravity, and it soon began to collapse in on him once more.

The heat wound tighter and tighter. It squeezed around Sans, and then managed to contract further, sinking beneath his ribs. He was on fire - it burned him from the inside out, pulsing and radiant like a nova burning in his chest. Pulsing, like an aching limb. Pulsing… pulsing… like a...

Sans was only dimly aware when the pain faded. He couldn’t see anything, but perhaps that was only because his eyes were closed, and he was far too tired to try to open them.

_So tired._

He was drifting - through what he couldn’t say - but that, too, was fine with him. He wouldn’t mind drifting like this forever. Nowhere to go. Nothing to do. Just… pleasant emptiness. Infinite and comforting.

But that wasn’t quite right, was it? There was something he needed to do. Something… important.

A thought nudged at him, and something else tugged at his chest.

What was it? He needed to remember. Sans sluggishly pushed his mind from the comforting warmth of sleep, and the pulling sensation on his body grew stronger. He could now feel himself moving through the void, being drawn downwards.

 _Papyrus_ , he remembered quite suddenly. At the thought the drift became a rush, and he was caught up in some torrential force that spun him through the nothingness. _Papyrus!_ he thought again, latching onto that single word. He was falling faster, faster, sure to shatter against whatever entity he was hurtling towards. He could feel it getting closer, the destination looming, and then-

 

 

The ground was cold and soft.

Sans was slow to rouse from his sleep, and even when he became distantly aware of his surroundings he found it so comfortable that he almost drifted back off. His body was sunk into a surface, refreshingly cool after the heat he’d previously endured. Recalling the heat, Sans’s mind fretfully came even more awake, and he let out low groan. His throat felt gravelled and all his limbs ached. Despite how tempting it was to simply lay there, embraced in the soothing cold, Sans knew he should get up.

The ground gave as he shifted. Sans grunted, digging his hand into the surface. The coolness crumbled through his grasp and fell out between his fingers. That was... odd.

Sans opened his eyes, only to squeeze them shut a moment later with a small hiss of discomfort. Everything was white, and his vision was painfully sensitive. Even so, he’d manage to catch a glimpse of his surroundings.

Was that… snow?

Sans had never seen snow before. The estate had been warm and humid most of the year - he could recall only one time in his childhood when a dusting had appeared overnight during a cold snap. But this… he’d never seen anything like this.

Carefully, Sans rolled onto his back. The snow crunched beneath his movements, and he let out a weak chuckle in spite of himself. _Snow._ Who would have thought.

Slowly this time, Sans cracked open his eyes.

Evergreens stretched above him, all their branches draped in white. Now that he was aware of them he realized he could smell the pine, as well as a clean, dewy scent that could only be the snow. Beyond the trees the sky appeared dark, though it was punctuated by spots of dim light that flickered like stars.

“guess we’re not in kansas anymore,” Sans smiled feebly.

Then he coughed, and tried to clear his throat. His voice felt strange - muted, almost, as if he were trying to speak underwater. But perhaps that had more to do with his hearing than his voice - he couldn’t be sure.

Sans decided it was time to get up. While lying there making snow angels was a tempting thought, he had more important things to be doing - like figuring out where he was, for one. And if Gaster-

Shit. Gaster.

“doc?” Sans called, his vision spinning as he sat up. Sans moaned around a bout of nausea, waiting until he had steadied before trying again. “are you there, gaster?” The forest remained quiet.

Perhaps Gaster had made it out. He had been ahead of Sans, after all - maybe Sans was the only one that had gone through. That was good. He hadn’t wanted Gaster mixed up in all of this, and he had enough to worry about as it was.

Resisting a yawn, Sans shook his head, trying to dislodge the last vestiges of drowsiness that seemed to be clinging to him. He needed a clear mind now more than ever. First he had to figure out where he was, assuming he was within reach of some kind of civilization. As much as he was enjoying the snow (which, to his surprise, wasn’t as cold as he’d thought it would be,) he could only survive for so long out in the middle of nowhere. Then he’d begin searching for any information he could get his hands on related to Papyrus. Surely their entry into… wherever this was… had resulted in some sort of distinct mark. A flash of light, a loud noise, a burst of wind - Sans couldn’t remember the exact moment he’d come through, but ripping a hole in spacetime had to leave _some_ sort of trace. Someone had to have noticed.

Sans was still running through his plan as he leaned forward, getting ready to push himself to his feet. Before he could stand, however, something caught his eye that made him stop mid-motion.

His hands were pressed into the snowbank, but something about it didn’t look quite right. Sans flexed his fingers, watching the snow shift around them. Instead of pale, fleshy digits showing through, he could only make out white on white. Perplexed, Sans lifted his hand from the snow. Then he screamed.

“oh, shit. oh shit!”

_He could see his bones._

Holy shit, how was that possible? How was he not in excruciating pain? What had even happened to his hand? The heat - he remembered the heat. Had he been burned so severely he couldn’t even feel it? (The fact that his bones were remaining together without the help of muscles and tendons didn’t even register to him.)

Sans decided he was in shock. That was the only explanation for why he hadn’t noticed the injury before. He needed to - to get help. Sterilize it or something. Hell, what did one even do in a situation like this? Was he going to have to get it amputated? Of course it needed to be amputated, that was a stupid thought - he couldn’t just grow back all his skin and muscle when he could _see straight through his fucking hand_. Sans grabbed his wrist, intending to cradle it to his chest - and then recoiled when he saw caught sight of his other hand. It was all bones, too. And even as he stared, frozen in shock, his eyes travelled up his wrists and arms.

“what,” was all Sans could weakly muster. His mind was reeling, trying to make sense of what he saw. There was no way he shouldn’t feel this. No way he should be _alive_ for that matter. You don’t just shrug off having your skin and muscle burned from your limbs. A manic giggle bubbled up from Sans. This wasn’t possible. There was _no way this was possible._

Sans held his hands out, flexing his fingers. “what the fuck,” he laughed, watching them move. This couldn't be right. He looked down at his legs - those were bones, too, of course. And his chest - he could see his ribs. Sans’s laughter grew uncontrollable, the panic overriding his reason. He raised his hands to his head, bone scraping over bone.

“crazy, definitely crazy,” Sans said, staring down at the snow as his laughs shook him. “ohhh, boy, i screwed this one up bad.” Sans ran his hands down the back of his neck, bumping over his exposed spine. “heh heh. i’ve lost it. cracked. this probably isn’t even real. a hallucination, or - or a dream. maybe it’s a dream. yeah. i got hurt in the jump and this is just a fever dream. i just gotta, gotta wake up somehow, heh heh.” Sans dug his fingers into his skull. “wake up, wake up!”

Sans began to tremble, his laughs turning into heaves. Part of him knew this was very much real, but he couldn’t let himself believe that yet. It was too much to take in, too much that went in the face of everything he understood to be true. Sans was too rational - too stubborn - to accept what was happening.

A heat began to grow in his chest as his manic ramblings continued. He wasn’t aware of the sensation until it had become quite hot, and he gasped as a sudden blue light shone out from between his ribs.

“oh no, no, not this again,” Sans moaned, his hysteria briefly overcome by dismay. He scraped at his chest, madly trying to pull the light away. Memories of the terrible heat he’d felt before came vividly back, and he tried to brace himself against the searing pain that was surely to follow. But this warmth was different than the fire he’d felt before. This sensation was milder and controlled, and even as he mentally shrunk from the internal heat, he felt it respond to his will. As the warmth began to bleed away, so did the light.

By the time the light faded, Sans found his breathing had calmed as well. “okay,” he said, trying keep himself from relapsing into panic once again. “this is okay. everything is just… just peachy.” His bones rattled as he shuddered in a deep breath.

Sans touched his face, exploring the features he already knew would be there. Or, rather, not there. In addition to the lack of flesh and blood, he now was without a nose, eyes, and even lips. How he was managing to talk was beyond him - but given the circumstances, it certainly wasn’t the strangest thing that had happened to him.

“at least you’re not dead,” he reasoned with himself. “could be worse, right? psychotic and alive is definitely a step up from being dead. heh heh. wow. this is so messed up.”

No matter how much he willed himself to wake up, however, the world in which he found himself continued to persist. Sans sat there for some time, waiting for a sign that he really was insane, or having an incredibly believable hallucination, or - hell, why not - trapped inside some kind of sick virtual reality. But the forest continued to quietly be a forest, and he continued to be a skeleton.

Sans only stirred when he felt his stomach growl.

“seriously?” he said, looking down at the empty cavern where his stomach should have been. “can i even eat?” His non-existent stomach seemed to think so (Sans waved a hand through his chest cavity to confirm there was, in fact, nothing there.)

“welp,” Sans said, finally pushing himself shakily to his feet. His bones clattered as he stood and he reached out to steady himself against a tree. “might as well play along. i guess. what can go wrong, right? heh heh.” After tearing a hole in spacetime and managing to lose most of his body in the process, he figured whatever else he ran into couldn’t be much worse. Sans glanced around the snowy woods, hoping to find some indication of a path. “...just as soon as i figure out where i am.”

“SMALL, NAKED SKELETON!”

Sans jumped at the sudden voice, having thought he was alone.

“ARE YOU LOST?”

Before he could turn around Sans froze, his heart fluttering in his chest. That voice… no, it couldn’t be. He wanted so badly for it to be true, but… but he didn’t trust himself. He wasn’t in his right mind - maybe it was just an extension of his delirium. Sans didn’t know what he would do if he looked and no one was there. He couldn’t deal with that. He couldn’t risk it.

“ARE YOU FEELING WELL?”

But it sounded _so real_. And Sans so badly wanted to turn around. He was only able to hold out for a moment longer before his resolve crumbled. Still not allowing himself to face the voice’s speaker, Sans took a breath, his throat constricting.

“papyrus?”

There was a pause. When the voice spoke again, it was softer and unsure.

“Sans?”

**Notes for the Chapter:**

> The brothers reunite!
> 
> What's this? A chapter that doesn't end with emotional or physical harm? I must be losing my edge. 
> 
> I never meant for this story to become so Sans-centric (though I can't help but love that guy,) so the next chapter will focus on Papyrus.


	10. Papyrus

**Summary for the Chapter:**

> A chapter in which we learn what Papyrus has been up to.

When Papyrus woke up he hadn’t known where - or who - he was. Some of it had come back to him since, but not much. 

Things of which he was aware: he was a skeleton. He had no clothes. He was in a snow-covered forest. And though he couldn’t particularly articulate why, he found this last fact quite exciting. Snow was  _ fascinating _ . It was squishy and cool and very fun to kick about. He could play around in the snow for hours - which, in fact, he did. 

His stamina waned before his enthusiasm. After rolling down a hill one too many times Papyrus found himself unable to get up, and stayed panting and elated in a small heap of snow. He wished he could share this happiness with someone. He felt like there was some in particular he wanted to share this with, but he couldn’t remember who. This thought itched at him, but the answer lay just out of reach. Lost in his thoughts and cushioned comfortably by the snow bank, it wasn’t long before he drifted off. 

It was the cold that woke him. What had been a pleasantly cool sensation before was now painfully cold, and Papyrus’s bones clattered as he shivered uncontrollably. Climbing to his feet was much more difficult than it had been before, not helped by the numbness that had seeped down to his very marrow. It must have taken some time for the cold to sink in - and with a small bit of uncertainty Papyrus realized he didn’t know how to get the cold out. 

Papyrus began to walk, recalling from somewhere that one should keep moving if they were cold. Aimlessly stumbling through the forest, he otherwise diverted his attention to picking out the snow that had become packed into the crevices between his bones. The snow that had previously seemed fun was now becoming quite troublesome - though, he assured himself, it was nothing the Great Papyrus couldn’t handle. 

Ah, yes. Papyrus. That was his name. 

The skeleton wandered for some time. Walking didn’t seem to help much, and now his bare feet were starting to ache; he decided shelter might be a better approach. This was easier said than done, however, given his limited line-of-sight in the closely packed woods. Papyrus frowned, trying to recall anything that might help him. 

_ Moss, _ a thought came back to him. Moss should grow on the damp side of the tree - so he should head in the opposite direct for warmth. Papyrus stopped to examine the nearest pine, but found all its branches draped in furry green substance. 

“YOU ARE NO HELP AT ALL,” Papyrus admonished. “BUT IT IS NOT YOUR FAULT, SO I FORGIVE YOU.” Looking around for something else that might trigger other memories of survival tips, Papyrus caught sight of the sky. It was far too bright out to be nighttime, but he could see lights twinkling overhead. He wasn’t sure what they were (stars was his first instinct, though that didn’t seem quite right,) but as he watched them he noticed something else. The sky had a gradient to it. While not entirely black, it appeared to grow more grey and distant in one direction, and more dark and close in the other. Papyrus wasn’t quite sure what this meant, except that he was close to something other than snow and woods. With little else to go on, Papyrus struck out in that direction. 

As he walked the sky seemed to get closer. The stars, too - if that was what they were - also appeared more large and bright. Both the sky and the stars gave the impression of curving towards the ground - a dizzying sensation Papyrus couldn’t make sense of until he stepped out from the treeline and found that’s precisely what had happened. Cautiously, Papryus walked up to the wall. Blue stones were embedded in its surface, shining brightly with an internal light. Papyrus craned his neck back once more, following the wall all the way up to where it became the ceiling. He was in some sort of cave, then. And judging by the distant pinpricks of light, the cavern was quite enormous. 

“BEAUTIFUL,” Papyrus said, his gaze drawn back to the luminescent gems. He gave one a tap, and then smiled. “THANK YOU, WALL,” he said, placing his hands on his hips as he looked left and right, following the rocky boundary to where it disappeared into the distance. “YOU ARE EXACTLY WHAT I WAS LOOKING FOR.” 

It didn’t take him long to find a cave sufficiently suited to his needs. The wall was pocketed with dozens of crumbling dens, all dry and mostly out of the snow. Of course finding a clearing was only half the battle; sitting on cold stone was not much of an improvement, but Papyrus already had a plan for that. 

Starting with moss and then going back for sticks and small branches, Papyrus gradually accumulated a store of materials he’d use for his fire. He didn’t question how he knew how to make a fire: it was just one of the things he knew. Like what a cave was, or that moss grew on trees. Firemaking knowledge was simply just a part of him. 

Yet starting a fire, in practice, was a different monster entirely. Everything was damp from the snow, and no matter how hard he rubbed two sticks against each other he couldn’t make them smoke. 

_ Flint, _ he remembered. If he could find some flint… but looking around he realized how foolishly hopeful that thought was. Papyrus was a little disheartened, but he was not ready to give up yet. He knew he could do this, he knew it! He returned to the stick and woodblock with renewed vigor. He just had to push it a little faster, and then surely it would be enough to light some of the kindling! Surely… 

Papyrus kept trying until his grasp was too weak to hold the sticks any longer. His tools clattered to the floor, leaving Papyrus panting and his arms shaking from the effort. He was no closer to starting a fire than when he started - and on top of this, he was now getting hungry as well. Papyrus was beginning to grow concerned, but he couldn’t give up yet. He would not be defeated by damp wood and a bit of cold! If only there was something else he could do. Some other way he could start the fire he hadn’t yet thought of. Better tools, maybe. Something.  _ Anything… _

With a small pulse of light, a blue bone materialized in front of him. “NYEH!” Papyrus exclaimed, surprised by the sudden manifestation. There was a light coming from his own chest as well, matching in color to the bone that hovered before him. He tried to make out where the light was coming from, but any way he turned his neck Papyrus couldn’t quite make out the light’s origin through his ribs. Papyrus looked back up at the bone, tilting his head. 

“HELLO THERE,” he said, raising his hand to grab the strange construct. The bone jumped to his grasp, which Papyrus found delightful. He turned it around in his hands several times before releasing it, whereupon it continued to hover. 

“WHAT ELSE CAN YOU DO?” Papyrus wondered aloud. He barely had to imagine the bone spinning in a circle before the construct did just that - and if he thought about it flying across the room, the bone complied. 

“NYEH HEH HEH! EXCELLENT,” he declared, looking back down at his pile of tinder. The bone moved to wedge of wood he’d been working on, slowly rotating as it waited for his next command. “NOW, LET’S TRY THIS AGAIN…”

 

Things became much easier with magic. The fire was simple to relight on the few occasions it went out, and Papyrus now had a reliable source of warmth at hand. Food, which had been next on his priority list, had solved itself when Papyrus happened upon a blackberry bush. True, it wouldn’t sustain him forever, but it at least bought him a couple days. And in that time he intended to explore. 

Papyrus’s cave was surrounded by a lot of trees. And snow. And… not much else, really. Apart from the berry bush, his most exciting find had been an old, beat up blanket, half frozen beneath a shelf of ice. This he brought back to his shelter, where he thawed it out until it was significantly less soggy. It was grey and full of holes, but it was better than nothing. Papyrus fixed it about his shoulders with one of his magic bones, wearing it like a cloak. As a form of insulation it wouldn’t do much, but at the very least he thought it looked quite striking. Papyrus lamented the fact that he didn’t have a mirror to confirm. 

It was difficult for Papyrus to tell how long he had been there. He slept a couple times and spent the rest of his waking hours finding more berries and exploring the area around his camp. It was on what might have been his third day there that he discovered a path. Had he not been looking for one he might have missed it - it was, after all, covered in snow like the rest of the woods. But the gap in the trees here was particularly wide, and when he really looked he could see the clearing wove away from the cave wall, heading somewhere deeper into the cavern. 

This was an excellent discovery! If there was a path, then there were most certainly other people at the end of the path. While Papyrus had found his fire and magic bones to be good company, he had admittedly been getting a little lonely as of late. Eager to strike out on this new adventure, Papyrus hurried back to his shelter to collect his small supply of berries and check that the fire was properly put out. (He was, after all, a responsible skeleton.) 

On his way back, however, a sharp  _ crack  _ shook the forest. A whisper of a breeze accompanied the noise, causing a light dusting of snowfall to shift off the trees. Papyrus paused, wondering what had caused the sound. It sounded like a snapped tree limb, or perhaps a snapped  _ tree _ given the volume. But what could cause a tree to snap? It was very curious. Curious enough, Papyrus decided, that he would delay his adventure to investigate. 

He only had a general direction to go on, which made searching for the source of the sound more difficult. Papyrus wished he at least knew what he was looking for - though he supposed anything that wasn’t just more snow and pine trees was likely to be the culprit. Walking in a switchback pattern to make sure he didn’t miss anything, Papyrus once more began to wander the woods. 

He passed the time fantasizing about what might have caused the noise. This new mystery was exciting! There were so many possibilities as to what it could be. Maybe he would find someone else to talk to. Or maybe it was an animal, and he could train it to be his pet. Or maybe it was something dangerous, like lightning - 

Papyrus shuddered, unsure why he had thought of that. The idea made him feel… uncomfortable. Papyrus decided to think about something else. Perhaps the sound had been caused by some ice breaking up. Maybe there was running water nearby, or...

Papyrus almost missed it over the crunching of his footfall. The sound was low and soft, perhaps only one or two dozen paces away. Papyrus stopped and listened. It was… a voice. A voice! He was sure of it. Papyrus honed in on the sound, following it to its source. 

“...play along. I guess. what can go wrong, right? heh heh.” 

The skeleton was leaning weakly against a tree trunk, his back to Papyrus. A skeleton - just like him! Well, not precisely like him - this one was much smaller - but even so. Papyrus grinned, eager to make his acquaintance. 

“...just as soon as i figure out where i am…”

“SMALL, NAKED SKELETON!” Papyrus cried, causing the other to jump. “ARE YOU LOST?”

The skeleton stiffened, but didn’t turn around. Curious. Perhaps he had not heard him. Of course he was only a few paces away, so Papyrus thought this might be unlikely, but there could be other reasons the skeleton wasn’t responding as well. Maybe he was cold, like Papyrus had been before he’d made his fire. 

“ARE YOU FEELING WELL?” Papyrus tried again, raising his voice. The small skeleton was shaking now - perhaps he really was cold. Papyrus took a step forward, about to go check on him, when the skeleton finally responded. It was the first time Papyrus clearly heard him speak. 

“papyrus?” 

The word hit him like a blow to his gut. That voice - _ that voice  _ \- Papyrus knew it like it were a part of him. It sent him reeling, keenly aware of a void in his mind he hadn’t known was there before that moment. It was important - he  _ had  _ to remember - had to fill that emptiness. Papyrus latched onto the voice and didn’t let it go, pulled hard against the half-remembered thought before it could slip away once more. Slowly, reluctantly, the memories relented, seeping back into Papyrus’s mind. 

“Sans?” 

That was all it took for them to come crashing back. His smile, his laugh, his stupid, wonderful puns - _ his brother _ \- oh, how could he have forgotten his brother? Where had he been? Why had they been separated - it didn’t matter. Sans was safe, and he was here, and Papyrus remembered him. 

At his name, Sans turned around. There was blue glowing at the rim of his eye sockets, threatening to spill over and run down his cheeks. He looked up at Papyrus, a mix of fear, relief and uncertainty on his face. Papyrus imagined he looked much the same.

“bro, is that really y-”

“SANS!” Papyrus swept his brother up into a hug, crushing him against his chest. “OH SANS, I’M SORRY, I’M SO SORRY!”

“y- _ you’re _ sorry?” Sans stammered, his arms pinned to his sides. “geez, pap, you’re not the one that should be sorry.” Sans knocked his forehead against Papyrus ribs with a shuddering sigh. “is this real?” he asked, his voice so soft Papyrus could barely make it out. “please be real.” 

Papyrus didn’t understand why Sans was asking that, but felt he should reassure him. “OF COURSE! REALLY REAL.”

“good,” Sans said, his shoulders shaking. “thank goodness.” 

The brothers fell silent, content to just hold each other and take comfort in the firmness of the embrace. Sans went limp at the physical contact, all tension drained from him as if he’d spent all his energy making it over some abstract finishline and now no longer had the motivation to go on. Papyrus didn’t mind doing all the hugging. He was so ashamed that he’d forgotten his brother, and a part of him was afraid that if he didn’t hold on tightly he might lose him again. He didn’t let go until he felt something wet against his ribs. 

“SANS!” Papyrus said, finally releasing the iron grip on his brother to hold him out at arm’s length. “YOU’RE CRYING! AND IF YOU CRY YOU’RE GOING TO MAKE ME CRY!” 

“what?” Sans sniffed. “no i’m not, skeletons can’t… oh…” Sans wiped his eyes, looking down at the glowing blue that streaked his hand. “heh. what do you know.” 

Reluctantly, Papyrus set his brother down. “ARE YOU ALRIGHT? YOU’RE NOT HURT?”

Sans chuckled, rubbing away the rest of his tears. “actually, given the circumstances, i’m doin’ pretty good.” He looked up at Papyrus with a genuine smile. “you know it’s kind of funny. i came all this way looking for you… but it was you that found me.” 

Happiness flooded through Papyrus in a warm wave, and he had to resist the urge to pull Sans into another embrace. “WELL, I’M NOT SURE HOW EXACTLY WE GOT SEPARATED IN THE FIRST PLACE, BUT THE IMPORTANT THING IS THAT WE ARE TOGETHER NOW.” 

Sans gave a weary nod. “i’m never going to lose you like that again, papyrus,” he said.  

“i promise.” 

 

 

**Notes for the Chapter:**

> Don't make promises you can't keep, Sans. *glances at the genocide run*
> 
> I know in most fanfics Papyrus's magic is orange, but because Sans and Papyrus both used blue magic in the game I decided for them both to be blue in this story as well. I'm trying to get this story to feed into Undertale as seamlessly as possibly, but it's growing increasingly hard to resist going off on tangents and just having fun with these characters. 
> 
> Speaking of fun, next chapter will be quite fluffy, and will be called: Snowdin.
> 
> Thanks for reading! Please feel free to leave comments, criticisms, and requests.


	11. Snowdin

**Summary for the Chapter:**

> In which Papyrus teaches Sans how to be a skeleton.

**Notes for the Chapter:**

> This chapter is pretty much just fluff, but I swear it's steering us back towards the plot. Sans just needs to come to terms with what's going on, first.

Sans ducked under a branch, hardly listening as his brother chattered away about a cave he had discovered. Papyrus had insisted on carrying Sans on his shoulders, something about worrying over his brother getting cold feet. Sans had almost made a joke - almost. Despite his elation over finding his brother, Sans still wasn’t quite back in a joking mood.

They were _skeletons_. And despite every rational bone in his body telling him otherwise, he was beginning to believe this was real. He didn’t know if he should be happy that they were alive, or horrified at what they had become. They certainly couldn’t go home looking like this. Sans felt a rush of guilt, the corners of his smile tugging downwards. Papyrus was like this because of him. What kind of a brother…

“SANS!” Papyrus cried. “ARE YOU EVEN LISTENING?”

“uh, sorry, bro,” Sans said. “it’s just… still a lot to take in. hey,” he said, changing the subject to get his mind onto other things, “what is this thing, anyway?” Sans picked at the disgusting, grey mat Papyrus had draped over his shoulders.

“IT IS A CLOAK, OBVIOUSLY!” Papyrus said, his attempt to swish it dramatically undermined by his brother’s presence. “DO YOU LIKE IT?”

Sans was a little skeptical. Was that mold on one of the corners? Well, he wasn’t going to be the one to let his brother down. “heh, it’s better than being naked, i guess.” He looked down at his body. “if skeletons can even be naked.”

“ WHAT?” Papyrus said. “OF COURSE THEY CAN! WHY NOT?”

“well i mean, there isn’t much to really cover up, you know?” Sans gestured vaguely.

“WHAT ABOUT OUR BONES?”

“i don’t think that counts.”

“WHY NOT?”

Sans didn’t have an answer for that. Maybe he was overthinking it.

“AND BESIDES,” Papyrus said, “YOU WILL DEFINITELY NEED SOMETHING TO KEEP YOU WARM OUT HERE!”

“it doesn’t feel that cold,” Sans noted.

“NYEH HEH! THAT’S WHAT YOU THINK AT FIRST!” Papyrus said. “BUT I KNOW BETTER. FEAR NOT, BROTHER, MY UNRIVALED SURVIVAL SKILLS WILL KEEP US BOTH SAFE!”

Sans laughed. “i don’t doubt it. good thing you were into scouts all those years ago. i remember you telling me i’d regret not joining, too. i guess now we know who was right about that.”

Papyrus, however, had fallen silent.

“bro?” Sans said, leaning over Papyrus’s head to try to get a look at his face. “you okay?”

“I’M SORRY, SANS,” Papyrus said with a sigh. “I DON’T REMEMBER ANY OF THAT.”

“oh,” Sans said, taken aback. “s-sorry, bro, i didn’t know.” Now that Papyrus mentioned it, Sans recalled him saying something to that effect before, though he’d been so caught up in the moment that he hadn’t paid it much mind. Now Sans frowned, wondering exactly what Papyrus had meant.

“what _can_ you remember?” he asked.

“THE FIRST THING I REMEMBER IS WAKING UP HERE IN THE WOODS,” Papyrus said. Sans couldn’t help but notice the dejection in his brother’s voice. “AND YOU!” he added more enthusiastically. “I REMEMBER YOU.”

“what about the machine?” Sans pressed. “gaster? the lab?”

Papyrus just shook his head. “I’M SORRY.”

“hey, don’t be sorry,” Sans said, giving his brother’s shoulder a pat. “you remember me, right? i bet the rest will come back, too.” Sans said it as much to comfort his brother as himself. The idea that Papyrus was suffering from amnesia was scary, but the last thing Sans wanted was for his brother to beat himself up over it. And maybe it wasn’t the worst thing that could have happened. At least his brother probably hadn’t had a panic attack about finding he had become a skeleton like Sans had.

His encouragement seemed to have worked, however. Papyrus nodded his head resolutely, and a skip worked its way into his step. “OF COURSE! I WILL GET THEM BACK NO MATTER WHAT. AFTERALL, I, THE GREAT PAPYRUS, WILL NOT BE DEFEATED BY - OH!” he interrupted himself, stepping out from the trees. “WE’RE HERE!”

“whoa,” Sans said, getting his first good look at the stone-studded wall. He leaned back, looking up to where the wall became the ceiling. “where are we?”

“A CAVERN OF SOME KIND,” Papyrus said, heading over to the wall. He lifted Sans off his shoulders and set him on the ground in front of a cave entrance. “SOMEWHERE UNDERGROUND.”

Sans watched the twinkling stones, thinking about how he’d first thought they were stars. His gaze drifted lower, alighting on his brother. Sans laughed.

“you’re even taller than me now.” It just wasn’t fair.

“OR MAYBE YOU ARE SHORTER,” Papyrus teased.

“heh, that is a distinct possibility, bro.” Sans turned to look into cave. “is this it?”

“OH YES!” Papyrus said, ducking into his shelter and beckoning his brother inside. “THIS IS THE CAVE I WAS TELLING YOU ABOUT. COME IN!”

“cozy,” Sans noted, looking around. More of the luminescent stones decorated the walls, their blue surfaces reflecting yellow and orange from the firelight. Papyrus was busy unfastening his cloak (the clasp seemed to vanish with a small glow of light, though perhaps Sans was just seeing things,) to set it on the ground before the fire pit. The brothers sat down on the old blanket, though it was only a mild improvement over sitting on the stone itself.

“gotta say, i’m pretty impressed,” Sans said, offering his hands up before the fire. He flexed his fingers, briefly distracted by the sight of his bones. He wasn’t sure he’d ever get used to that. “i wouldn’t have been able to put any of this together.” The fire felt distantly warm, but not hot. It was similar to how the snow had felt cool, but not cold. Sans edged a little closer, trying to absorb more of the heat. Maybe bones just didn’t exchange heat like skin did. Of course, Sans reminded himself, they shouldn’t be able to feel temperature at all. But things seemed to have stopped following the laws of nature as he knew them.

“NONSENSE!” Papyrus exclaimed. “I AM SURE YOU WOULD HAVE DONE JUST FINE ON YOUR OWN. IT WASN’T SO HARD, REALLY.”

Sans watched his brother as he talked. It was so surreal. What was producing his voice? Or moving his jaw? Sans also noticed small pinpoints of light in the sockets where Papyrus’s eyes were supposed to be. Did Sans look like that, too? Curious, Sans stuck a finger in his eye.

“ow.”

“SANS!” Papyrus said. “WHY DID YOU DO THAT?”

“honestly, bro,” Sans laughed, “i don’t know what i was expecting.”

“HMMM.” Papyrus rubbed his chin. “YOU ARE ACTING VERY STRANGE, SANS. ARE YOU FEELING WELL? DO YOU NEED TO TAKE A NAP?

Sans stifled a yawn and the mention of a nap. He hadn’t quite shaken off the weariness he’d woken up with, but he couldn’t let himself rest just yet. After weeks of not knowing if his brother was even alive, Sans wanted to spend as much time with Papyrus as possible - even given the state they were in.

“nah, paps, I’m fine,” Sans tried to reassure him. “Just feeling kind of, uh… hungry,” he ended lamely. It was technically true, even if it wasn’t the most prominent thing on his mind.

“OH!” Papyrus said. “THAT I CAN MOST CERTAINLY HELP WITH.” Reaching into one of the darker recesses of his cave, Papyrus produced a handful of blackberries. “I SHOULD HAVE REMEMBERED SOONER! I WAS ALSO RATHER HUNGRY WHEN I FIRST WOKE UP.”

“wow, you really _have_ planned for everything,” Sans said, gently picking up one of the berries. Without the give of flesh, he felt like he was in danger of squishing it between his finger bones. “where did you even get these?”

“I FOUND A BUSH OF THEM WHILE SEARCHING THE AREA,” Papyrus explained. “HOWEVER THERE IS NOT MUCH LEFT NOW. WE WILL HAVE TO FIND SOME OTHER SOURCE OF FOOD SOON… BUT WORRY NOT! I DISCOVERED A TRAIL JUST BEFORE I FOUND YOU - AND IT IS A VERY LUCKY THING YOU APPEARED WHEN YOU DID, OR I MIGHT HAVE ALREADY LEFT TO SEE WHERE THE TRAIL GOES, BUT… SANS?” he asked, his brother obviously distracted. “WHAT IS IT?”

Sans was rolling the berry around in his palm. “i, uh,” he chuckled looking up at Papyrus in embarrassment. “well, i mean… it sounds kinda dumb, but… how do you eat it?”

Papyrus stared at Sans. “WHAT?”

“it’s not that unreasonable of a question, right?” Sans said, slightly flustered. He gestured aimlessly. “like, where does it even go? we don’t have tongues or throats or stomachs-”

“SANS,” Papyrus tried to interrupt.

“won’t it just fall out the bottom of my jaw?” Sans continued. “and even if I bite it then there’s gunna be berry juice all over, and then what do i do?”

“SANS,” Papyrus tried to stop him again. “JUST EAT THE BERRY.”

Sans eyed it suspiciously. “but how-”

“BROTHER. PUT IT IN YOUR MOUTH. AND CHEW IT.”

Sans still didn’t look convinced. Papyrus threw his hands in the air before grabbing one of the blackberries and popping it in his mouth. He chewed and swallowed. Sans tilted his head, waiting to see if anything fell out of his rib cavity. When nothing happened, Sans dubiously looked back down at his own berry. Well, it would be an experiment at the very least.

Sans squeezed his eyes shut (another impossible act he’d have to investigate) and stuffed the berry in his mouth. Somehow it didn’t fall out, so he chewed it, distantly tasting the sting of citrus. Like with the fire and snow his senses seemed dulled, and while he could still taste the berry it was definitely less flavorful than it should have been. Distracted by these thoughts, Sans hardly noticed when he swallowed the berry and it simply… vanished.

Sans peaked an eye open, noticing his brother watching him and smiling triumphantly. Sans drummed his fingers together, thinking.

“okay but for the record, i just want to say that makes absolutely no sense.”

Papyrus laughed. “IF YOU SAY SO, BROTHER. WOULD YOU LIKE MORE?”

“yes,” Sans admitted, his nonexistent stomach growling. Papyrus transplanted the pile of berries on the blanket between them, and the brothers began to eat.

“i don’t know how you do it,” Sans said, shaking his head as he took another berry. “you’re just so level headed about everything. i just can’t let go of how weird this is.”

“HMM,” Papyrus consider. “I SUPPOSE… I KNOW WHAT THINGS ARE ACTUALLY LIKE, EVEN IF I DON’T KNOW HOW THEY SHOULD BE. BUT THAT’S OKAY BECAUSE I CAN DEAL WITH THINGS AS THEY ARE BETTER THAN I CAN DEAL WITH THINGS THAT MAY OR MAY NOT BE. DOES THAT MAKE SENSE?”

Sans had to think about it. “yeah,” he said, slowly smiling once more. “yeah, that makes sense.” Sans chuckled. “you’re so cool, bro. i bet nothing fazes you.”

Now it was Papyrus’s time to think. “ACTUALLY,” he said, “THERE WAS ONE THING THAT SURPRISED ME!”

“really?” Sans asked. He smirked, jabbing a playful finger at his brother. “no way, i don’t believe it.”

“IT’S TRUE!” Papyrus said. “HERE, I WILL SHOW YOU!” Papyrus raised a hand and a bone materialized before him.

“holy crap!” Sans jumped.

“LANGUAGE!”

“what the heck is that?!” Sans leaned forward, his shock quickly overcome by curiosity.

“IT’S A BONE, SANS.”

“yeah, but, like, it’s _floating_!” Sans said. “and blue. how are you even doing that?”

Papyrus shrugged. “I DON’T KNOW. I JUST THINK ABOUT IT AND I CAN DO IT!”

“that’s crazy,” Sans said, poking it. The bone rotated lazily. “it’s like… it’s almost like magic.” As kids, they’d always wished they could do magic. Countless days were spent running around the woods while shooting invisible spells at each other with sticks. Coming to terms with the non-existence of magic had been a sobering experience, but now… Well, Sans didn’t know what else to call it.

“I BET YOU CAN DO IT, TOO!” Papyrus said.

“you think?” Sans considered. “i don’t know…”

“YOU COULD DO IT!” Papyrus insisted. “I’M SURE IF YOU TRIED YOU WOULD FIGURE IT OUT RIGHT AWAY!”

It was a tempting thought. Could he really just will something into existence like that? It sounded crazy, but he wanted to give it a shot. Before he could try, however, something else caught his eye.

“whoa, papyrus,” Sans said, staring at his brother. “you’re glowing.”

“HM?” Papyrus said, looking down at himself. “WHAT DO YOU MEAN?”

“your chest,” Sans said. “there’s a light in there or something.” He leaned closer to get a better look.

“OH, YES… YES I THINK I SEE.” Papyrus frowned. “WHAT IS IT?”

“i dunno,” Sans said, scooting closer to look through his brother’s ribs. “it’s like… it kinda looks like a heart.” A heart made of light.

“A HEART?” Papyrus considered. Then he gave a nod. “THAT MAKES SENSE.”

Sans laughed, sitting back. “sure. why not.” He tried to peer through his own ribs, curious if he had one as well, though as far as Sans could tell there was nothing there. Then again he hadn’t noticed it in Papyrus before, either. Perhaps it only appeared occasionally, like when Papyrus had summoned a bone. The thought made Sans recall something else, a moment back in the forest when a blue light had been shining through his own chest. It had only lasted for a few seconds, but there had definitely been something there. What could have triggered it? His emotions? The memories had largely been overshadowed by Sans’s panic, so it was hard for him to recall.

“IT’S BEEN VERY USEFUL,” Papyrus said, banishing the bone with a wave of his hand. “BUT IT WON’T HELP FIND FOOD, UNFORTUNATELY.”

“oh, yeah,” Sans said, looking down at their significantly depleted pile of berries. “sorry about that.”

“NONSENSE!” Papyrus said. “AS I WAS SAYING BEFORE, I HAVE A PLAN.”

“oh?”

“YES! THERE IS A PATH, YOU SEE,” Papyrus said. “AND AT THE END OF THAT PATH I AM SURE WE CAN FIND SOME PEOPLE WHO WILL HELP US!”

Sans laughed. “sounds like a solid plan to me.” He didn’t have any better ideas, though the prospect of running into other people made him nervous. What on earth would they think when they saw a couple of animated skeletons? Papyrus didn’t seem to recognize the precarious situation they were in, so Sans would have to make sure they tread carefully. If they found anyone at all, this is.

Papyrus noticed Sans’s thoughtful frown. “I WAS HOPING TO EXPLORE SOON, BUT… IF YOU LIKE WE CAN REST FIRST. YOU STILL LOOK TIRED, BROTHER.”

“yeah,” Sans said, rubbing his neck. He couldn’t seem to shake it off. Maybe Papyrus was right and a nap would do him good. If his brother was going to head somewhere populated, however, Sans didn’t want him to be on his own. “just a bit worn out is all. but if you’re going to explore i want to come with.”

“REALLY?” Papyrus said, his eyes lighting up. “HOW EXCITING! NYEH HEH HEH, IT WILL BE AN ADVENTURE, THEN! NOW? SHOULD WE GO NOW?”

“sure, bro,” Sans said, chuckling at his brother’s eagerness. He slowly climbed to his feet, stretching his limbs with a series of rattles and pops. “lead the way.”

Papyrus was all too happy to comply.

Resecuring his cloak about his neck (this time Sans saw Papyrus was using one of his magic bones to keep the cloak pinned together,) and making sure the fire was properly extinguished, Papyrus struck out into the woods once more. Sans trailed after, watching his bare feet crunch into the snow.

Once he got over the fact that his feet were all bones, the sensation was kind of enjoyable. He experimented as he walked, sometimes trying to step in Papyrus’s wide tracks, and other times kicking large ruts in the powder. Sans couldn’t help but find it fun. Despite everything, snow was a new experience.

Papyrus noticed Sans scuffing about. “REALLY, SANS, I EXPECTED YOU TO BE MORE SERIOUS ABOUT THIS. SNOW CAN BE VERY DANGEROUS!” He stopped, kneeling down to scoop some snow into his hands. Sans tilted his head, unsure why Papyrus was being so solem over a bit of frozen water. Papyrus squeezed his fingers around the snow, packing it down into a ball. “YOU SEE? IT CAN GET PACKED TOGETHER QUITE TIGHTLY. WHICH IS BAD IF IT GETS STUCK IN OUR BONES. ALSO,” he said, lifting up the ball for Sans to see. “IT CAN BE USED FOR… AMBUSH!” The snowball struck Sans right in the middle of his face.

There was a moment of shock as Sans stumbled backwards, slapping his hands to his face. Then he chuckled darkly.

“oh my god,” Sans said, wiping the snow out of his eyes. “you did not just do that.”

“NYEH HEH HEH HEH!” Papyrus laughed, bounding away. “MY TACTICS ARE UNRIVALLED.”

“you know this means war, brother,” Sans said, laughing as he crouched down to pack together a snowball of his own. “you know not the ruin you have invited!”

Another lobbed snowball stuck Sans’s shoulder before he even had his first one ready. “ah, i see,” Sans said, rounding on his brother, who was hurriedly making another one. “trying to overpower me with sheer numbers. that’s one strategy.” He grinned mischievously. “but i prefer quality over quantity. take this!” With everything he had, Sans wound up and threw, sending his projectile careening towards Papyrus.

It fell two feet short.

“shit.”

“LANGUAGE!” Another snowball rained down on Sans.

“i fear the odds are stacked against me,” Sans said, grabbing a handful of snow and packing it down as he retreated behind a tree.

“NHEH HEH! HE FLEES BEFORE SUPERIOR FORCES!”

“this is a tactical retreat!” Sans cried, peeking out from behind his tree to throw his snowball at Papyrus. It missed again. “the day is young!” Snow impacted the tree right next to Sans’s face.

“HMM, WELL, LET’S SEE HOW LONG YOU CAN HOLD YOUR NEW GROUND!” Papyrus sprinted towards Sans’s shelter, two snowballs in hand. Sans abandoned his tree, taking a snowball to the back just before he was able to slip behind another one. Sans waited until Papyrus came after him again, jumping out to throw his ball when he knew his brother would be too close to miss.

Papyrus summoned a bone and swung it like a bat, smashing through Sans’s snowball and causing it to disintegrate into a cloud of loose powder.

“what?!” Sans said. “that’s cheating!”

“NYEH HEH HEH! YOU ARE JUST JEALOUS YOU DID NOT THINK OF IT FIRST!”

“i don’t even know if i can- hey!” Sans jumped away from Papyrus’s other snowball. “alright, then, you want to play dirty? i can play dirty.”

Sans scooped together another snowball, packing it as he ran for cover. One of Papyrus’s attacks narrowly missed as Sans ducked. “you see, brother, you failed to account for my secret weapon.”

“SECRET WEAPON?” Papyrus paused, and Sans took the opportunity to make his throw; Papyrus sidestepped it with little effort. “YOU DON’T HAVE A SECRET WEAPON.”

“do you _snow_ that for a fact?” Sans grinned. A snowball smacked into the tree Sans was hiding behind. “heh heh, that was an _ice_ throw.”

This produced an audible groan.

“what’s the matter, paps?” Sans said, returning the attack with a throw of his own. “ _snow_ comeback?”

“SANS, YOUR SECRET WEAPON BETTER NOT BE TERRIBLE PUNS.”

“uh oh, sounds like i’m on _thin ice_.”

“THIS IS GETTING ABSURD!” Papyrus dove around Sans’s tree and pelted him with three snowballs in rapid succession. Sans laughed, attempting to fend off the onslaught.

“ _chill out_ , bro!” Sans tried to get away, but only ended up falling into a snow drift. He covered his face as Papyrus stormed over with an entire armful of snow. “heh heh heh, i thought you’d be _cool_ with- oof!”

Sans pushed the snow away from his face, finding the rest of him properly buried. Papyrus flopped down in the drift next to his brother, letting out a dramatic sigh.

“YOU JUST HAD TO RUIN THE MOMENT.”

“heh heh.” Sans turned to look at his brother. “you’re smiling.”

“NYEH HEH HEH.” Papyrus made no effort to cover his amusement. “I ASSURE YOU IT IS ONLY A VICTORY SMILE.”

“sure, bro,” Sans chuckled. The brothers fell silent, their light pants fogging the air as they caught their breath. Sans looked back up at the sky, watching the distant lights twinkle against the cave wall. There was a fluttering in his chest, and if it wasn’t for the snow he wondered if he would see a heart there, faintly glowing. He felt…something. An emotion he hadn’t let himself feel since Papyrus had been snatched up by the machine that fateful night. It wasn’t relief or affection - both of those Sans had felt in full the moment he’d heard his brother’s voice again.

As Sans’s eyelids dipped lower and his breathing slowed, he realized what it was. Happiness.

Sans was happy.

 

 

**Notes for the Chapter:**

> Even if Papyrus isn't entirely sure what's bothering Sans, he's at least aware something's going on. And if there's one thing Papyrus is good at, it's keeping his brother grounded. 
> 
> Thanks for reading!


	12. A Friendly Face

**Summary for the Chapter:**

> Sans and Papyrus meet the residents of Snowdin.

**Notes for the Chapter:**

> Wow, so, this one's a lot longer than my typical chapters, and I probably should have just broken it up into two, but I really wanted to end it at a certain spot so here it is. 
> 
> Not my most polished chapter, and I'm not terribly happy with the pacing, but oh well. We gotta progress the plot.

“SANS.”

Sans woke to a methodical swaying. Apart from the crunch of snowy footfall, it was peacefully quiet. He opened his eyes to find himself looking down Papyrus’s back.

“SANS,” Papyrus said again.

“uh. what?”

“YOU FELL ASLEEP,” Papyrus explained. “I’VE BEEN CARRYING YOU.”

“oh,” Sans yawned, trying to blink away the fatigue. “sorry, bro. i didn’t realize…” Sans rubbed his eyes, attempting to reorient himself.

“DON’T BE SORRY, YOU SEEMED VERY TIRED,” Papyrus said. “I WOULD HAVE LET YOU SLEEP LONGER, BUT THERE IS A PERSON AHEAD.”

“what?” Sans said, suddenly much more awake. “where?” He struggled to turn around, and Papyrus hoisted him off his shoulder, setting his brother on the ground.

“JUST DOWN THE HILL,” Papyrus pointed. Sans followed his direction.

“uhhh,” Sans squinted after a moment of silence. “is... is that…?”

“A PERSON,” Papyrus repeated.

“but…” Sans stared a moment longer. There was a cottage at the bottom of the hill, and a clothesline in the backyard. A kid was playing in the snow and their mother was hanging up clothes on the line nearby.

“...but that’s a five-foot tall rabbit, right?” Sans couldn’t stop staring.

“OH,” Papyrus said. “YES, IT APPEARS SO.”

“a five foot tall rabbit that’s wearing clothes,” Sans continued, rubbing the side of his skull. “and doing laundry.”

“YES THAT DOES APPEAR TO BE WHAT SHE IS DOING.”

“right,” Sans said. Maybe he still hadn’t woken up all the way yet, but he honestly didn’t know what to think. Would anthropomorphized rabbits be open to the idea of animated skeletons? Or, as he expected might happen back on his world, would they be seen as demonic creatures and lynched on the spot?

“SANS?” Papyrus questioned. “WHAT ARE YOU THINKING?”

“uh.” Sans decided not to share his thoughts. “i was just thinking… we could probably use some clothes of our own.”

“OH!” Papyrus exclaimed. “EXCELLENT IDEA! I WILL GO ASK.”

“what? wait, no, that’s not what i-” but Papyrus was already bounding down the hill. Sans smacked his hands against his face, then peeked through his fingers to watch.

“shit,” Sans muttered as the rabbit person looked up in alarm at the skeleton skipping down the slope towards her. Sans doubted she posed much of a threat - Papyrus was, after all, two heads taller than the rabbit in question - but he was worried regardless. He certainly couldn’t catch up in time to be of any use, and even if he could he wasn’t exactly the most physically imposing creature around. Sans groaned. This was exactly the kind of situation he’d been hoping to prevent!

Papyrus was talking to her now. What were they saying? It was probably fine, but what if things escalated? What if someone got hurt? Sans would be useless. Geez, he wished his brother hadn’t just run off like that.

In his agitated state, Sans didn’t notice the blue light that began to form in his chest. His focus was still on his brother, who was gesturing wildly. The kid - also a rabbit - had hopped over to their mom to hide behind her skirt. Mothers were protective, right? Did Papyrus appear threatening? Sans wished he was closer-

And then he was.

“oof.” Sans fell face first into the snow.

“AH, SANS!” Papyrus exclaimed, looking down at his brother. “I WAS JUST TALKING ABOUT YOU!”

“uh, yeah,” Sans said, trying to figure out what had just happened. He looked up at a rather shocked rabbit woman, just as surprised as himself. “heh, just thought i’d drop in.”

“ANYWAY,” Papyrus said, “THIS VERY FRIENDLY INNKEEPER WAS JUST SAYING SHE MIGHT HAVE SOME CLOTHES FOR US!”

“Sure do,” the rabbit said, tilting her head curiously at Sans as he climbed to his feet and brushed some of the snow off. “Though finding something in your size,” she pointed to Papyrus, “might be difficult.”

“oh,” Sans said, glancing sidelong back up the hill. Hadn’t he just been…?

“...that would be great,” he said, smiling nervously as he met the rabbit woman’s gaze. This was weird, so weird. “but, uh, we don’t have any way to pay you…”

“Oh, no, don’t worry yourself over that,” the rabbit woman said, folding her arms across her chest. “Customers leave clothes at the inn all the time. It’s no fur off my back. Now my _sister_ ,” the Innkeep laughed, “you wouldn’t catch her dead giving stuff out for free. Come on,” she said, shooing her kid ahead of her and gesturing for the skeletons to follow. “You both must be freezing out here. I’ve got some things in the back you can try.”

 

\---

 

In little time at all the brothers were happily clothed. Though Sans hadn’t felt particularly cold, the clothes made him feel a little more comfortable and less self conscious. Getting the clothes on had been an interesting adventure of skeletal anatomy; his bones kept snagging on the cloth, and pants with zippers had proved entirely useless. Luckily there had been some sweatpants he’d managed to cinche above his pelvis, and plenty of shirts that fit. He settled on a cozy sweatshirt that covered most of his bones while his brother squeezed into a tank top - the only shirt that didn’t look absurdly small on him. For once, Sans was grateful for his smaller stature.

“So are you two travellers or something?” the Inkeeper asked as the brothers returned from her her storage room.

 _Time travellers,_ Sans thought with a smile. “heh, yeah, something like that. thanks again for your help,” he added, hoping to deflect the question.

“Not a problem,” the Inkeeper waved him off. “Say, you mentioned you didn’t have any gold… you guys gotta plan for that?”

“GOLD?” Papyrus asked. “OH NO, WE MOST CERTAINLY DO NOT HAVE ANY GOLD.”

“No food either, I bet?” the Inkeeper said, looking the brothers up and down. She shook her head. “Tell ya what, you can stay here for a night while you get situated.” She dug a paw into her apron as she spoke, then held it out to the brothers. “And here’s a couple G. It’s not much, but you should be able to grab something at Grillby’s. Maybe a couple somethings - he’s a real pushover,” she winked.

“oh, uh, no, i don’t think we should,” Sans said, hold his hands up at the offered money. Geez, was that _gold_? “uh, really, thanks, but that’s so much-”

“Nonsense,” the rabbit said, grabbing Papyrus’s hand instead and stuffing the gold into his grasp. “If it makes you feel better, think of it as advertizing. Tell your friends about Snowed Inn, Snowdin’s premier hotel!”

“OF COURSE!” Papyrus agreed as Sans sunk further into his jacket. “WE WILL TELL EVERYONE TO COME HERE, BECAUSE IT HAS THE BEST HOST!”

The Inkeeper grinned, swatting at Papyrus’s arm. “That’s the spirit. Well, if that’s it, then you boys best be hopping along. I’ve got a business to run, after all.”

“oh, sure,” Sans said, edging towards the door. “thanks again for all this, really.”

The Inkeeper waved as she made her way back towards the front. “Enjoy your visit!”

 

“WHAT A KIND LADY!” Papyrus said as he and Sans began to explore the town. “I AM SO GLAD WE RAN INTO HER!”

“yeah,” Sans said, watching the other residents of Snowdin as they passed. They all appeared to be animals, like the Inkeeper. The brothers drew some looks as they passed, though Sans got the impression it was less due to surprise at seeing walking skeletons and more due to curiosity about a couple of new faces. “she was… surprisingly friendly.” He hoped that was a trend that would continue.

“THIS IS A VERY NICE TOWN, TOO!” Papyrus observed. “MAYBE WE CAN FIND SOMEWHERE TO LIVE HERE!”

“what?” Sans gave a start. “live here…?” He hadn’t been thinking that far ahead. As a first step he’d just been hoping to figure out where they were, and after that? Well. Eventually he’d figure out how to get them back to their world, but the steps in between then and now were still a little hazy.

“IT SEEMS MUCH NICER THAN THE CAVE,” Papyrus said.

“oh- oh, right,” Sans said, lightening up a little. “yeah, i guess we’ll have to find a place to stay after tonight. good call, paps. maybe we can ask-”

“LOOK!” Papyrus cried. “AN IGLOO!”

Sans looked, then chuckled. “seems a little small.”

“PERHAPS THERE ARE BIGGER ONES!” Papyrus said. “AN IGLOO WOULD BE FUN TO LIVE IN!”

“i dunno, bro,” Sans said. “you don’t think living in there would make you feel a little _ice-_ olated?”

“SANS!” Papyrus rounded on him. “WE WERE HAVING A GOOD DAY. DON’T START THIS NOW!”

“sorry, papyrus,” Sans said. “i guess i _slipped up_.”

Wordlessly, Papyrus turned and began to march away.

“aw, come on,” Sans said. “don’t give me _the cold shoulder_.” He chuckled when Papyrus’s shoulders heaved in an aggravated sigh. At least this felt normal.

It didn’t take long for Sans to catch up, though he felt a little winded from the jog. Geez, he was in worse shape than he thought - though how skeletons could get fit was beyond him. Sans nearly ran into his brother when Papryus came to an abrupt stop.

“GRILLBY’S,” Papyrus said, pointing to the building. “THIS IS THE PLACE WE WERE INSTRUCTED TO VISIT, YES?”

“uh, yeah, i think so,” Sans agreed. “want to check it out?”

“OH COURSE!” Papyrus said. “IF WE ARE GOING TO EXPLORE THE WHOLE TOWN, WE SHOULD FIRST ENSURE WE ARE FED!”

“can’t argue with that,” Sans said. He gestured towards the building. “after you, bro.”

The inside was a strange juxtaposition of the familiar and bizarre. It appeared much like any other pub, complete with a jukebox and a neon sign hanging from the wall, though its patrons were far more otherworldly. There were a couple animal monsters - a bird, a hamster, and… was that a fish? But there were also stranger creatures, too, like a being that seemed to be made entirely of teeth, and the bartender, who appeared to be on fire. No, that wasn’t right, Sans thought, unable to keep from staring. He was _made of_ fire.

“heya,” Sans said, crossing the room to sit on one of the barstools. He was acting significantly more relaxed than he felt, all too aware of the eyes that followed him and his brother across the room. Hopefully the affected confidence would temper their curiosity. Assuming everyone else was as friendly as the rabbit monster they’d run into.

The bartender nodded in greeting, preoccupied by a glass he was polishing. Papyrus sat down next to Sans, appearing rather cramped on the tiny stool.

“so, uh, got any menus around here?” Sans asked. The brief silence that had accompanied their entrance fell away as the monsters turned back to their meals and smalltalk.

The bartender shook his head.

“Burgers and fries,” a bird creature at the bar said. He swiveled on his seat to face the skeletons. “Grillby doesn’t use menus since it’s easy to remember.”

“oh, thanks,” Sans said. Burgers and fries sounded strangely normal for a town populated entirely by monsters, but hey, he was willing to roll with just about anything by now.

“i’ll take a burger, then,” Sans ordered. “paps?”

“HMM,” his brother seemed skeptical. “IS THAT ALL?”

Grillby stepped aside and gestured to the shelved of drinks that decorated the wall.

“Most people come here for the drinks,” the bird monster explained.

“OH,” Papyrus said. “THAT IS NOT EXACTLY WHAT I-”

“come on, bro,” Sans said, hoping not to annoy the barkeeper within the first five minutes of entering his establishment. The last thing Sans wanted was to draw more attention. “beggars can’t be choosers. you want a burger, too?”

“I SUPPOSE,” Papyrus agreed. He didn’t seem terribly thrilled with the place.

“hey,” Sans said, trying to distract him. “it’s gotta be better than blackberries, right? and i’m getting mine with _extra_ tomatoes and ketchup.”

That seemed to have the desired effect. “OH, MINE AS WELL!” Papyrus said. “AT LEAST, EXTRA TOMATOES, PLEASE!” Grillby nodded as he set the cleaned glass back on a shelf, then wordlessly left through a back door. Soon enough the smell of cooking wafted back into the main pub.

“I’m Red Bird, by the way,” the bird creature said to Sans and Papyrus. “You guys new here?”

“YES,” Papyrus said at the same time Sans said “no.”

“just passing through,” Sans added after exchanging a look with his brother.

“From the capital, then?” A punkish looking hamster at the other end of the bar spoke up. “Yeah, it’s getting pretty crowded there. Not surprised more city folk are showing up in Snowdin.”

“...yeah,” Sans said, not sure how much he could say or ask before it was obvious he had no idea where they were.

Luckily, Papyrus had him covered. “WE ARE ON AN ADVENTURE!” Papyrus explained. “WE’VE DECIDED TO EXPLORE EVERYWHERE WE CAN SO WE CAN FIND A PLACE TO LIVE!”

To Sans’s relief, the other monsters nodded sympathetically.

“You can get pretty restless around here,” the fish monster agreed. “I lived in Waterfall for a long time, but moved here when I needed a bit of fresh air.”

“Better than Hotlands,” Red Bird added with a laugh. “Don’t know how anyone can live in that heat.” Grillby returned from the back with Sans and Papyrus’s burgers. “No offense, Grillby.”

Grillby, as usual, did not reply and instead set the plates down in front of the two skeletons. The smell made Sans’s stomach growl.

“thanks, man, that was really fast.”

Grillby shrugged and went over to the sink, filling a couple glasses for the brothers as well.

Sans picked up his burger, glancing towards Papyrus who’d been uncharacteristically silent. His brother was picking at the bun.

“what’s up?”

“IT’S RATHER…” Papryus rubbed two of his finger bones together with a grimace. “...GREASEY. I DON’T LIKE HOW IT GETS INTO MY JOINTS, SANS.”

“just wipe it off,” Sans said with a shrug. It was a long-standing point of contention between the brothers. While Sans could - and often did - thrive in messy environments, Papyrus couldn’t stand it. Sans considered himself adaptable - Papyrus called it sloppy.

“WHAT AM I SUPPOSED TO USE TO CLEAN- OH MY GOD, SANS, NO!”

Sans was wiping his hand off on his pants in demonstration. Papyrus visibly winced. “WE JUST GOT THOSE!”

“we can clean ‘em later,” Sans said, smiling from his brother’s apparent discomfort. “but as you said, we need to be fed before we can do any exploring.” Lifting his burger in cheers, he was unable to suppress a chuckle in anticipation of his brother’s reaction.

“ _bone_ appetit!”

 

\---

 

They were only halfway through their meals when the pub’s front door slammed open. Several cloaked and weapon-toting dogs stepped inside, followed closely by a blue, amphibious monster in a shining set of armor.

“Human sweep,” she barked. “By order of the royal scientists. We’ll keep this quick.”

Sans nearly dropped what was left of his burger. “w-what?”

Grillby wiped his hands off on a rag, stepping out from behind his bar as the dog monster spread out and began sniffing their way through his pub. He made his way over to the armored fish woman.

“...Undyne…” Grilly’s voice was quiet, made of soft whispers and crackles of flame.

The knight turned towards him. “Hey, Grillz, long time no see!”

“...This is quite disruptive,” Grillby said, unmoved.

Undyne laughed. “Well, that’s what hunting humans looks like! We should be quick, though, I doubt you’re harboring any fugitives.” Her grin was full of pointed teeth.

One of the dogs sniffed, turning its head in Sans and Papyrus’s direction. “What’s that?”

The other dogs turned towards the brothers as well. Sans leaned away as they sniffed closer, while Papyrus patted one on the head. “HELLO!”

“...My customers,” Grillby began, but Undyne cut him off.

“Yeah, look, I know it’s a hassle. And I promise we won’t break much! ‘Sides, I said we’ll be out of here soon; we still got all of Snowdin to search.” Undyne grimaced.

“...What is going on, Undyne?”

The dogs were still circling Sans and Papyrus. “Smells like,” one of them said. “Smells like…”

“Bones!” another one cried.

“Oh! Yes, smells like bones.”

“hey, paws off,” Sans said, swatting at one of the dogs who was getting a little too nosey. Papyrus, on the other hand, had summoned a magic bone, and looked as if he were about to try to get them to play fetch.

“Like I said,” Undyne said, still talking to Grillby, “we’re here by order of the royal scientists. And if Alphys and Gaster say there might be humans in the area, then-”

“ _Gaster?_ ” Sans cried, startling the dogs that were still sniffing him and his brother curiously. Undyne raised an eyebrow at the outburst, craning around Grillby to get a better look.

“Yeah. What’s it to you?”

“doctor gaster?” Sans repeated. There was no way it could be a coincidence.

“You know him?” Undyne asked. Grillby sighed, seeing as how the conversation no longer concerned him, and returned to his bar.

“i... i think so,” Sans said.

“YOU DO?” Papyrus echoed.

“Well, good for you,” Undyne said, ignoring Papyrus’s question and looking away from Sans. “Now if we’re done here - hey!” she shouted at the dogs, finally noticing their fixation with the skeletons. Papyrus guiltily dispelled his magic bone. “What are you guys doing? Get back to work! Those obviously aren’t humans. Jeez, are you guys blind or something?”

“Actually,” one of them started, before Sans cut him off.

“w-wait,” he said. “humans, right? we, uh, might have some information about humans.”

All eyes in the bar snapped towards Sans.

“WE DO?” Papyrus asked.

Undyne seemed equally surprised. “Seriously? Why didn’t you say so earlier! Well, what is it? Spit it out!”

“it’s, uh, sensitive information,” Sans said, the excuse sounding weak even to him. “we have to talk to gaster about it directly.”

Undyne squinted in suspicion. “Why don’t ya just tell me and then I’ll go tell him?”

“it’s, um,” Sans hesitated, his mind racing for an explanation. “well, it has to do with the variable nature of einstein-rosen bridges and internal inconsistencies in a closed timelike curve which probably led to a non-orthogonal quantum state in which-”

“Ugh, okay, enough with the nerd talk,” Undyne cut him off. “You’re just as bad as they are. And all that has something to do with the humans?”

“yes, definitely,” Sans said.

The amphibian scratched the back of her head, thinking. Sans held his breath.

“Alright,” Undyne finally agreed. “You two come with me. And you guys,” she pointed an accusing fingers at the dogs. “Stop slackin’ off! I expect this whole area to be swept by the time I get back.”

“thank you!” Sans said, getting up to leave. Papyrus seemed confused as to what was going on, but stood up with his brother. Sans was just turning away from the bar when he remembered they hadn’t paid.

“oh!” he said, quickly turning back to the counter and gesturing for Papyrus to take out the gold they had been given. “sorry, i don’t know how much it cost, but this is all we’ve got.”

Grillby looked down at the money.

“...Will you be back?”

“uh, sure, i guess so,” Sans said.

Grillby slid the coins back over to the brothers.

“...I’ll open a tab.”

 

\---

 

Undyne grumbled all the way to Hotlands, and when they got there it became clear why.

“you, uh, gunna be okay in all that?” Sans asked, noting the heavy streams of sweat that streaked down the guard’s face.

“Of course I am!” Undyne panted, her metal armor clanking with each step. “This is nothing!”

“IT IS QUITE IMPRESSIVE ARMOR!” Papyrus observed. “I IMAGINE WEARING IT HERE IS QUITE HOT!”

“Yep,” Undyne said shortly. “Pretty freakin’ hot.”

To Sans it only felt humid and warm, though like with the cold he expected that was only because it hadn’t sunk in yet. “is it always this hot here?”

Undyne barked out a laugh. “That’s why it’s called Hotlands, nerd. Ugh, finally,” she added. As they rounded a bend in the road, the Lab could be seen before them. Despite being built into the walls of the cavern, it was an all-too-familiar sight for Sans. He looked up at his brother, hoping it might trigger some memories, but Papyrus seemed unaffected.

The three let out a sigh of content when the laboratory’s doors opened and a blast of cool air washed over them.

“Alright,” Undyne said, leading them over to an elevator. “I’m going to drop you two off with the doctor and then, uh, let Alphys know you’re here.”

“WHO’S ALPHYS?” Papyrus asked as they stepped into the elevator.

“You don’t know who Alphys is?” Undyne seemed a little offended. “She’s the other royal scientist! You’ll probably want to talk to her, too, right?”

“uh, not really,” Sans said, having no idea who that was. “just gaster is fine.”

“Oh,” Undyne said, glancing away. “W-well, I should probably let her know you’re here anyway. Just to be thorough!”

“sure,” Sans said, a little confused. After a few more moments the elevator came to a stop. Undyne pushed her way out first, though as she passed Sans swore he could see a subtle blush on the back of her neck.

Undyne led them down a series of hallway before coming to stop at a closed office door. “He’s just through here,” she said, knocking once on the door and opening it before anyone had a chance to answer.

“Doctor Gaster,” she said, stepping inside. She saluted, then quickly stepped aside so Papyrus and Sans had room to enter as well. “Reporting back from Snowdin. No luck finding any humans, yet.”

“Yet?”

Sans stared at the man sitting behind the desk. He hadn’t bothered looking up since Undyne entered, his face buried in a stack of papers. Scribbling something down on one of the papers he was examining, he paused to snap his fingers and a second set of purple hands manifested in the air beside him. These set about organizing another pile of papers, and as Sans watched he realized there were at least three other sets of hands doing various other tasks as well.

Sans was so distracted by the magical display that it took him longer than he would have liked to realize the man sitting behind the desk was also a skeleton. But Sans was already certain about who he was.

“We hadn’t finished sweeping the area, yet,” Undyne admitted.

“Well, If That’s All, Then I Am Quite Busy,” Gaster said, waving a dismissive hand at Undyne. “Let Me Know If You Find Anything Else.”

“Actually,” she said, “that’s why I’m here. We didn’t find any humans, but these skeletons said they might-”

“What?” Gaster said, his head jolting up. At the same moment he caught sight of Sans and Papyrus, and a look of shock passed over his face.

“Stars,” he said, standing up. “Is It… Is It Really You?”

“hey, doc,” Sans said, smiling weakly. “guess we weren’t the only ones that got _boned_ , heh.”

“Of Course,” Gaster said, passing a hand over his face. “I Should Have Expected It. Stars, I Never Thought I Would See Either Of You Again.”

“Er,” Undyne said, clearly uncomfortable with the reunion. “So, I’m gunna go then…”

“Leave,” Gaster agreed, waving her away. He took a couple steps towards the brothers, then stopped as if unsure what to do with himself. Sans imagined Gaster was examining them in the same way he was examining Gaster. His skull was cracked, with a line creeping up from his right eye socket and down from his left, but apart from his less fleshy appearance it was the same Gaster Sans knew. He wore a black lab coat and glasses that were balanced precariously on the front of his face, likely held in place where they hooked through the bones at his temples. Gaster wrung his hands - the bones clattering against each other - in a familiar gesture Sans had come to recognize as meaning Gaster was deep in thought.

It wasn’t until Undyne edged away that Sans let himself sag with a relieved weariness.

“what’s going on, doc?” Sans said. “you’re some kind of royal scientist? and everyone is monsters, and we’re - we’re freaking _skeletons!”_ Sans scraped his fingers over his skull. “i am so insanely lost.”

“Oh Dear,” Gaster said, looking between the brothers. “Well, That’s A Lot To Answer At Once. You Two Should Probably Make Yourselves Comfortable.” He gestured a couple of chairs in the corner of the room that were filled with even more papers. “Oh.” Waving at the chairs, a couple of the disembodied purple hands flew over to make room. “How Long Have You Been Here?”

“i don’t know,” Sans admitted, looking at Papyrus. “maybe a day or two?”

“I THINK IT HAS BEEN THREE OR FOUR DAYS SINCE I WOKE UP,” Papyrus supplied.

“I See,” Gaster said. “Then I Have A Lot To Explain.” He paced for a moment as he thought, then stopped and clasped his hands behind his back. Gaster gave the brothers a sad smile, which sent an unnerved shiver down Sans’s spine.

“There Is So Much I Want To Ask And Say,” Gaster said, “But There Is Something I Should Probably Make Clear First.” He paused.

“You May Have Only Been In The Underground For A Few Days, But For Me It’s Been Over Six Years.”

 

 

**Notes for the Chapter:**

> I'm starting to regret my capitalization choices with our skeleton friends, ha ha. 
> 
> Should I throw a tag in there for Undyne? She's not really a main character but idk.
> 
> Next chapter will be Gaster POV, tentatively named "You've Got Some 'Splainin' To Do"


	13. You've Got Some 'Splainin' To Do

**Summary for the Chapter:**

> Sans and Gaster talk about the nature of souls and magic. Some questions are answered. More are asked. Gaster has a visitor.

Despite his composure, Gaster was awash with emotions. Relief, joy - even a bit of sadness. He’d very nearly hugged the brothers when they’d walked in the door, before he’d reminded himself that the reunion was rather one-sided. Even so, it was hard for him to remain as calm and collected as he appeared.

Stars, they were _alive_.

“what?” Sans said after a moment of silence. “what do you mean it’s been six years?”

Gaster was not surprised by the disbelief. “We Were Messing With The Fabric Of Spacetime, Sans,” he said. “It Shouldn’t Come As A Complete Shock.”

“but,” Sans floundered. “but we went through together! how is that possible?”

“I Wondered That Myself For A Long Time,” Gaster admitted. After waking up alone, he’d had all sorts of theories about what might have happened to Sans. The one he’d eventually and regretfully settled on was that his companion must have died while switching realities (or at least, he’d ended up so far in the future or past that one of them was functionally dead to the other.) Clearly, however, that conclusion had been false, which meant one of his other explanations were more likely.

“I Believe It Has To Do With The Nature Of This World’s Magic,” Gaster explained. “It Operates On Intent, Which Might Explain Why You Came Through So Close In Space And Time To Papyrus. Your Desire To Find Your Brother Altered The Coordinates To Where You Otherwise Would Have Arrived.”

“i… i’m not following any of this, doc,” Sans admitted. “magic? intent? this is all just…”

“You’re Right,” Gaster apologized. “I Think I Need To Take A Step Back.” But he barely knew where to begin. There was so much to explain - so much for them to discuss.

Before he could collect his thoughts, however, Papyrus stood up. Fidgeting, he glanced towards Gaster, before looking back towards his brother out of habit. “SORRY,” he said. “BUT… I AM ALSO NOT FOLLOWING ANY OF THIS. IT SEEMS YOU TWO KNOW EACH OTHER, AND I THINK I SHOULD PROBABLY KNOW YOU, TOO, BUT I DON’T. AND… THERE IS PROBABLY A LOT YOU TWO WANT TO TALK ABOUT THAT I WON’T UNDERSTAND. I DO NOT WISH TO BE IN THE WAY.”

“you’re never in the way, bro,” Sans was quick to say. In the same breath, however, he addressed Gaster’s confused look with a pained grimace of his own. “he… he can’t remember anything from before he got here.”

“Oh,” Gaster said, the implications slowly sinking in. Nothing? Then… he didn’t even know who Gaster was. Gaster’s face fell as he bowed his head towards Papyrus in apology. “I’m Sorry. I Didn’t Know. We Used To Be...” Friends? He wasn’t sure that was the right word for it. “...Colleagues.”

“I SEE,” Papyrus nodded, though he didn’t appear any less uncomfortable.

“If You Would Like,” Gaster offered, “You Can Join Undyne And Alphys In The Break Room. They’re Likely Watching Anime.” It was a custom the two had developed whenever Undyne visited the lab. They’d even convinced Gaster to sit through a couple episodes, but the shows were not typically to his taste.

“Besides,” Gaster added, “There Are Some Things I’d Like To Discuss With Sans In The Meantime.”

“OH, YES, UNDYNE SEEMED NICE,” Papyrus agreed, quick to jump at the opportunity to excuse himself.

“are you sure?” Sans asked. He seemed more reluctant for Papyrus to leave than Papyrus was. “you’ll be okay?”

“OF COURSE I WILL BE FINE!” Papyrus said, some of his bravado returning. “IF WE SHOULD BE WORRIED ABOUT ANYONE, IT IS YOU!”

“He’ll Be In Good Hands,” Gaster said, smiling at the brothers’ concern for each other. He’d almost forgotten how close they’d been. “Shall We Go Find Them, Then? I Can Lead The Way.”

Sans seemed hesitant, but was quick to follow along once it became clear Papyrus and Gaster would be leaving. Gaster felt a brief pang of guilt for putting Sans in this situation, but soon dismissed it; Papyrus seemed uncomfortable - perhaps even overwhelmed - and Gaster was more interested in talking to Sans, anyway. It was for the best.

 

Sans lingered even after they arrived at the break room and Gaster had explained the situation.

“you sure you want to stay?”

“IT SOUNDED LIKE IT WOULD MOSTLY BE… SCIENCEY STUFF,” Papyrus said with a slight grimace. “AND UNDYNE SAID SHE DOESN’T MIND!” he added. “SHE HAS EVEN OFFERED TO TEACH ME HOW TO SPAR!”

“Hell yeah!” Undyne said, jumping up on the break room’s worn-out sofa in her excitement. “Beating up new people up is way better than science!”

“Um, G-Gaster.” Alphys leaned around Undyne from where she was still sitting on the couch. “I-is this s-something important? Do you n-need any help?”

“No, Nothing To Worry About,” Gaster assured her. “Just… Catching Up With An Old Friend Is All.”

“O-oh, okay then…”

“If That’s All, Then… Sans?” Gaster prompted, causing the smaller skeleton to jump.

“right, yeah, i’m coming,” he said. “see you in a bit, paps.” He stepped out of the room with a wave, but hesitated by the door until Gaster motioned that they should begin walking. Sans looked back once, but followed.

“Are You Alright?” Gaster prompted. “Papyrus Will Be Fine, You Know.”

“oh, yeah, i’m sure he will be,” Sans said, stuffing his hands in his pockets. “it’s just… it’s the first time we’ve split up since i got him back.”

Gaster felt another small pang of guilt. “I’m Glad You Found Him.”

Sans nodded. “me too…” He hesitated. “i guess, i feel kinda bad just leaving him in the dark on all this.”

Gaster considered this. “If He’s Suffering From Amnesia, As You Say, Then I Think Waiting Is For The Best. There Is Already… A Lot To Explain. I Wouldn’t Want To Overwhelm Him. Besides,” he added, seeing Sans was little assured. “His Memory May Return In Time. No Need To Rush It.” Secretly, however, he had his own doubts about Papyrus’s memory. He would let Sans come to conclusions about that on his own.

“you’re probably right, doc,” Sans sighed. “i just… wish i could help somehow.”

“Seems Like You Could Use Some Help Of Your Own,” Gaster smiled wryly. “I’m Sure You’re - How Did You Put It - ‘so insanely lost?’”

Sans chuckled. “gaster, you don’t even know the half of it.”

“On The Contrary,” Gaster said, stopping in front of an elevator. Accustomed to carrying too much to press the button manually, Gaster instinctively manifested a hand to push it for them. Sans watched the magical construct with rapt attention, though made no comment. “I Am Sure I Know Exactly How You Feel.”

“ah shit, sorry, you’re right, g,” Sans said, looking up at Gaster with guilt plain on his face. They stepped onto the elevator and the doors quickly closed behind them. “you’ve already been through all this. geez, and you went through it alone, too.”

“Yes, Well.” Gaster adjusted his cuffs in place of meeting Sans’s gaze. “I Won’t Pretend It Was Easy.” Stars, how he’d panicked when he’d first arrived. He may very well have lost it if he hadn’t had the pain to keep him grounded. Gaster absently rubbed at a crack along his ulna. “But I Was Able To Make Do. I Even Made A Place For Myself Here.”

“doc,” Sans said. “where even is _here_?” The elevator whirred to a stop, the sudden heaviness indicating a quick deceleration. The two stepped out onto another level, this one far hotter than the previous area. The air wavered from the heat, though by now Gaster hardly noticed it. He led them out onto a platform that spiderwebbed away in a series of catwalks. Beneath them was a distant, red haze from which the occasional hisses and viscous pops could be heard.

“Welcome To The Underground, Sans,” Gaster said, spreading his arms. “More Specifically, Welcome To The Core.”

“what the hell,” Sans said, cautiously peering over one of the railings with a chuckle. “This looks like some kind of villainous lair.”

Gaster laughed. “A Mad Science Facility Would Be More Accurate. Come On,” he gestured, striking out on one of the suspended paths. “My Personal Lab Is This Way. The Core,” he explained as they walked, “Is The Source Of Most Of The Underground’s Energy. Geothermal. It Might Not Be The Most Safely Placed Of Facilities, But We Have To Make Due With What We’ve Got. And That Is Because We Are All Trapped Down Here.”

“trapped?” Sans repeated, though his eyes were glued to his footing rather than Gaster.

“In The Underground,” Gaster nodded. “Honestly You’ve Probably Travelled Through Most Of It On Your Way Here. It May Be Giant As Far As Caverns Go, But For Containing All Of Monster-Kind It’s Become A Bit Cramped.”

“monster-kind?” Sans asked. “you mean like werewolves and mummies, and…”

“Skeletons?” Gaster offered with a wry smile. “Well, It’s Not Exactly What We Had Envisioned Back On Our World, But Yes, That’s Effectively It.”

“so, there’s no humans on this world?” Sans asked. Then, taking a stab, he guessed, “is that why we became skeletons?”

Gaster laughed. “You Know, I Think It Would Be Preferable If That Were The Case. But The Answer Is No - Far From It. Humans Do Exist In This Reality.” He Paused. “Though It Is Unlikely You Will Ever Meet One.”

“i’m… not keeping up.”

“Well, It’s Quite Simple,” Gaster explained. “Using Some Type Of Arcane Soul Magic, The Humans Of The Past Created A Barrier To Seal All Monsters Away In The Underground. While A Human Soul May Pass Through The Barrier As It Pleases, It Would Take Seven Human Souls To-”

“no, doc,” Sans panted. “i mean _i’m not keeping up._ ”

Gaster turned around to find Sans leaning heavily against the railing, beads of sweat forming on his skull. “Oh. Oh! I’m Sorry, I Always Forget How The Heat Affects Others.”

Sans shook his head. “nah, the heat’s not too bad. just, tired is all. did a lot of walking before we got here, and it feels like i’ve been running on empty all day.”

Gaster’s brows furrowed in thought. “Just Today? Or Ever Since You Arrived In The Underground?”

Sans thought about it. “...yeah, i guess it’s been like this since i woke up here. i thought a nap would help - and it did for a little bit, anyway - but i can’t seem to shake this weariness. why, what are you thinking?”

“Just… A Theory,” Gaster admitted. “Sans, There’s A Few Tests I’d Like To Run When We Get To My Lab - Just A Physical, Really. Is That Alright?”

“uh, yeah, sure, doc,” Sans agreed, though he looked more confused than anything. “what’s this about?”

Gaster nearly brushed him off, but seeing as Sans still could use a minute to catch his breath, he relented.

Gaster touched one of the cracks in his skull. “These Were There When I Woke Up. The Scars Have Healed Some Over Time, But Never Went Away Completely.” Nor were the fissures limited to his skull, though his clothing did a good job of concealing the rest.

“geez… i’m sorry, doc,” Sans said. “does… does it hurt?”

“Not Anymore,” Gaster lied. “I’ve Grown Quite Used To Them. But The Point Is That Jumping Realities Has Proven To Be A Dangerous Process. I Came To This World With Severe Damage To My Body - And Papyrus With Severe Damage To His Memories.” Sans winced at Gaster’s wording. “I Just Want To Be Sure There’s Nothing Wrong With You As Well.”

Sans gave a nervous laugh. “well I’m feeling pretty _sans_ ational at the moment, heh.”

Gaster smiled, though he was more concerned than entertained. “Even So, I’d Like To Run A Few Tests.”

“sure, doc,” Sans agreed, his gaze slipping away. Gaster tried and failed to read his expression. “i think i’m good now. lead the way.”

It only took another minute or two to reach Gaster’s lab. In that space the conversation returned to subject of souls, of which Sans still appeared to be somewhat skeptical.

“i mean, come on, g,” Sans said, tapping his skull. “you’re a rational guy. who we are’s not some abstract, intangible thing. that’s what the, uh…” Sans trailed off mid-thought, realizing the dilemma even as he spoke. “...that’s what the brain is for.”

“And Skeletons Don’t Have Those, Do They?” Gaster chuckled. It was fascinating to watch Sans reach all the conclusions Gaster had come to years ago. He actually seemed much more receptive to some of the ideas than Gaster had been, though Gaster stubbornly chalked that up to having a more scientifically ingrained mind. “So Where, Then, Is Our Mind?”

“alright, doc,” Sans said, admitting defeat. “i’ll bite. if our mind is in our soul, then where’s a person’s soul?”

Gaster paused before the door to his lab, turning back to face Sans. He had planned on introducing the concept more gently, but Sans’s question was too tempting to leave unanswered.

There was a soft _ping_ and a purple light radiated from Sans’s chest. Gaster gestured, gently tugging Sans’s soul from his ribcage. Sans’s eyes grew wide as he stared at the floating heart, then he slowly raised his hands to cup the exposed organ.

“heh. well, what do you know.”

Gaster released his magical hold, and Sans’s soul faded back to a light blue. “That’s You,” Gaster said. “Your Mind, Memories, Magic. Everything That Holds Your Bones Together. It’s As Powerful As It Is Fragile; Keep It Safe.”

Sans nodded, unable to look away from the floating heart. “you know, even though i don’t have anything more than your word to go on, somehow i believe you. it just feels… right. does that make sense?” He gently bounced the soul in his palms. “how do you…? ...oh.” As he spoke, his soul disappeared from view.

“As I’ve Said, Sans,” Gaster said, turning back to his lab to push the door open. “Magic Operates On Intent. To Summon Or Banish Your Soul, All You Need To Do Is Think It. Similarly,” he said, forming a pair of magical hands to hold the door open as they walked inside, “Magical Constructs Can Also Be Created At Will.”

“that seems pretty _handy_ ,” Sans grinned as he followed Gaster inside. The lab was large - reminiscent, almost, of the one he’d had back in his reality. Half the room was filled with an array of computers and servers, while the other half crowded with various experiments that were either running or in the process of being assembled. One notable absence was the time machine; though he attempted to be subtle about it, Gaster couldn’t help but notice when Sans glanced up, and shrugged a quiet sigh of relief.

“...so, doc,” Sans said, wandering around the room as he explored the machines and tests that littered the lab. Gaster went over to one of his tables and began rooting around as Sans spoke.

“...do you think we had, you know, souls back on our world, too?” Sans tapped at a vial of glowing red liquid. “you think they were there the whole time and we just couldn’t see ‘em?”

“I’m Not Sure,” Gaster admitted. Where had he put that blasted device? It had only been a few months since he’d last used it, but things tended to disappear in the lab’s clutter. “It’s Possible. I Have A Different Theory, However.”

“yeah?” Sans prompted. “let’s hear it, doc.”

“Do You Remember What It Felt Like When You Were Between Realities?” Gaster asked. “In The Void.”

Sans shivered. “i don’t think that’s something i’ll ever be able to forget. it was pretty… _gut wrenching_ , heh.” His laughter sounded strained.

“The Worst Pain I’ve Ever Experienced In My Life,” Gaster put it bluntly. “Due, No Doubt, To Over Eighty Percent Of My Body Undergoing Disintegration. Do You Wonder What Happened To The Rest Of That Mass?”

“i hadn’t thought about it,” Sans said. “i guess it was just… lost. wherever we were.”

“And What If It Wasn’t?” Gaster suggested. _Come on Sans, you’re smarter than this._ “What If It Was Conserved?”

“well matter can’t be destroyed, so…” Sans looked up at Gaster in surprise, a hand raising instinctively to his chest. “no way… seriously? but that would be, like, an _insane_ amount of energy! i mean, is that even possible?”

Ah, now he was getting it. “‘The Only Way Of Discovering The Limits Of The Possible Is To Venture A Little Way Past Them Into The Impossible.’”

Sans laughed nervously. “i feel like i’m carrying a bomb around in my chest.”

“Come, Now, Sans,” Gaster said. “Your Soul Is Much More Elegant Than That.”

Sans just shook his head. “so you’re saying that’s why we’re like… this? that most of our body became… became our soul?”

“Yes, Effectively.” Ah, here it was. Gaster brushed a few papers aside, using a couple of his hand constructs to dig the device out from where it had been buried on one of his desks. “I Believe This Reality Necessitates A Physical Soul, And So When We Came Here Without One Our Bodies Had To Improvise. Luckily For Us,” Gaster added, “That Makes Us Fairly Powerful Among Monster-Kind.”

“how’s that?” Sans was still fingering his chest nervously, and didn’t appear at all assuaged by the strange contraption Gaster had produced. Sans found a mostly-empty swivel chair and sat down, watching Gaster set the machine up.

“Monsters Are Made Almost Entirely Of Magic - Which Is To Say, Energy,” Gaster explained. “And Our Magic Pool Is Rather Large Due To Its Source. Of Course, We Also Have More Mass Than Most Monsters.” Gaster tapped at a bone in demonstration. “Though Like The Rest We’re Still Only Held Together By Magic.”

“you say that like we’re not human,” Sans said, cocking an eyebrow.

“As Far As This World’s Magic Is Concerned,” Gaster said, flicking a switch on and getting the machine to light up with a faint green glow, “I Stopped Being A Human Six Years Ago.”

Sans laughed weakly, though quickly tapered off when it became clear Gaster was not joking. “wait, doc, you’re serious?”

“If You Still Doubt It, There Is One Simple Experiment To Put The Matter To Rest,” Gaster said. “Try To Step Through The Barrier. Only Human Souls Can Leave The Underground.” Years ago he’d attempted to pass through it himself, and the results had been as disappointing as they were expected. He’d show Sans later and let him try it for himself if he still needed proof. In the meantime, however, there were other experiments to run; Gaster plugged a wand-shaped sensor into the machine.

Sans was still processing what Gaster had said. “i know we don’t look human anymore, but i guess i never thought that, well, that meant we _weren’t_ human. that our… our very dna was changed.”

“Monsters Don’t Have DNA,” Gaster said. “Not Physically, At Least.”

“... that information is stored in the soul instead,” Sans guessed.

“Now You’re Getting It,” Gaster said. “And Speaking Of Souls, I Need To See Yours Once More.”

“oh, um, sure,” Sans said, eyeing the equipment Gaster had set up. “uh.... what exactly are you going to do?”

“I’ll Just Be Checking Some Basic Readings,” Gaster said. “It’s Completely Non-Invasive. It Will Read Off Your Magic Stores, Health Levels, That Sort Of Thing. I Expect Your Numbers Will Be Similar To Mine, Given Our Shared Circumstances, But It Can’t Hurt To Be Thorough.”

Sans nodded, looking down at his ribs as he cupped his hands. A moment later the was a small flash of blue, and his soul was hovering above his palms. “heh.” Sans looked up at Gaster. “thanks for being so _patient_ with me.”

Gaster smirked, stepping closer with the apparatus. “Some Things Never Change, I See. Now Hold It Up.” Gaster used a couple of his magical constructs to wheel the machine’s display closer, though he was careful not to touch Sans’s soul with the magic for fear of skewing the results.

Sans shivered as Gaster touched the tip of the dowel to his soul. It took a moment for the screen to flash on, but once it did a series of fields began to populate. Sans watched the readout curiously.

“what’s it say?”

Gaster frowned, humming to himself. “Most Of These Readings Don’t Make Sense,” he admitted, removing the wand from Sans’s soul and knocking a hand against the side of the machine. Gaster flipped the machine off and on before he tried testing Sans’s soul again. “Damn. It Might Be Broken.”

“health: 1/1,” Sans read. “magic: 9999. heh, well i don’t know what it’s supposed to be, but that doesn’t sound right.”

Gaster again removed the instrument from Sans’s soul, summoning his own. “It Certainly Isn’t. Pity. It Was A Useful Machine, Especially For Medical Examinations.” Gaster tapped the rod to his soul, and the screen once more populated. This time the numbers had changed.

That was strange.

“health: 2928/3200. magic: 4860,” Sans again read. “is that a lot? that sounds like a like a lot.”

“It Is Above Average,” Gaster admitted, briefly removing the wand from his soul to refresh the screen. This time his health displayed 2927/3200, but all other statistics remained the same.

“is this accurate?” Sans asked.

“I Believe So,” Gaster said, perplexed.

“why did your health decrease?”

“It Is A Consequence Of My Scars.” Gaster waved off the question. “It Is Of Little Concern So Long As I Heal Regularly.” This was something he’d rather not have Sans focus on, so he changed the subject. “However, It Appears The Machine Is Working Properly Now. Let’s Try It Again.”

Once more Gaster tapped the wand to Sans’s soul, and once more the screen populate. The two skeletons stared at the readouts.

Health: 1/1. Magic: 9999

“i don’t understand,” Sans said. “one health? what does that mean? is that bad?”

“ _Stars_ , There’s No Way This Can Be Right,” Gaster said. Only one HP. How was that even possible? And his magical potential was off the scale…

“it was just working for you,” Sans pointed out. “it’s gotta be right. but what does it mean?” he asked again.

Gaster shook his head. “I Have No Idea. I’ve… I’ve Never Seen Anything Like This. One HP - Even Young Monsters Don’t Have Health This Low. Of Course - No Wonder You’ve Been So Tired. But Why...?” He skimmed the charts, his finger trailing down the screen. “Ah…” he paused, tapping the screen. That wasn’t good, but it had to be it.

“what is it, doc?” Sans said, letting out a nervous chuckle. “you’re kinda freaking me out here. what’s wrong with me?”

“Your Bone Density Is Far Lower Than It Should Be,” Gaster observed. “Less Than Half Of Mine. I Retained Almost Twenty Percent Of My Original Matter When I Came Through The Portal, However It Seems That You May Only Be Five To Ten Percent Of Your Original Mass. Which Also Explains Why Your Magic Reserves Are So Much Larger.”

“that’s… good?” Sans nervously suggested.

Gaster shook his head. “This Puts You In A Very Precarious Situation, Sans. If We Can’t Find A Way To Raise Your Health, You Are Going To Have To Be Exceptionally Careful. Breaking A Bone Might Be Enough To Unravel Your Physical Form. _Stars_ , It’s A Miracle You Even Made It Through The Portal.”

“o-oh,” Sans said, his soul dissolving as he lowered his hands. The skeleton stared blankly down into his lap. “so i, uh… you’re saying i almost died?”

Gaster grimaced - he hadn’t meant to be so blunt about it, but what Sans said was true. Under slightly different circumstances Sans might have entered the time machine and not come out the other side.

“I’m Sorry, Sans,” Gaster said. “This Was Not What I Had In Mind When I Wanted To Catch Up.”

Sans shook his head. “no, don’t be sorry.” He looked up with a grin once more plastered on his face. Sans appeared sincere, but Gaster couldn’t help but wonder if it was just an act. Most people wouldn’t be taking this so well. “i don’t have _thin skin_ , heh. i’m glad you told me - i’ll try to be careful.”

“I’m Sure Between The Two Of Us We Can Figure Something Out,” Gaster said. “There _Are_ Ways To Increase Health…” Though apart from natural ability and growth, the methods Gaster had in mind were not likely to appeal to Sans. “...But Perhaps That Can Wait For Another Day. I’d Wanted To Give You A Tour Of The Facilities As Well, But I Think That, Too, Can Wait Until Tomorrow.”

“that sounds good to me,” Sans said, slipping out of his chair. “i’m beat. but, uh… I really would like to tour the lab tomorrow.”

“Of Course,” Gaster said, perking up a bit. “You’re Always Welcome In My Lab.” Gaster paused, remembering a time on a different world when he’d said much the same. It was a lifetime ago. “And You’re Always Welcome As My Assistant, Sans.”

Sans’s eyes lit up. “really? it seems like you’ve got a lot of guys already working for you here, so i wasn't sure…”

“Nonsense,” Gaster said, waving away the notion. “You Were The Best Assistant I Ever Had. Besides, I Imagine You And Your Brother Will Be Needing A Place To Stay - And A Way To Pay For It.”

“that sounds great, gaster!” Sans said, but a moment later a frown passed over his face. “...actually,” he amended, “i’d rather… not have papyrus work here. not that i’m not grateful - i am! - but, uh… i mean, he probably wouldn’t like it anyway, and i don’t mind working for both of us, so…”

“Oh Course, Of Course,” Gaster said, quick to reassure Sans. It was no great mystery why Sans wouldn’t want his brother working in one of Gaster’s laboratories again. “Then… I’ll Be Seeing You Tomorrow?” They began to walk towards the lab’s door.

“definitely,” Sans smiled. They stopped at the door, and Gaster could feel the Core’s heat bleeding through the cracks. “…gaster?” Sans added, fidgeting with the sleeve of his hoodie. “i just wanted to say… i’m really glad you’re okay. and i’m sorry for getting you mixed up in this. really, really sorry.”

For the second time that day Gaster nearly pulled Sans into a hug, and for a second time he managed to refrain. Instead he hesitantly raised a hand, then rested it on Sans’s shoulder after a light pat. “It Was My Creation, And I Knew The Risks Involved. There Is Nothing To Forgive, Sans.”

And even if there were, it had been years since he’d given up on trying to go back. This was his home now, and likely it would become Sans and Papyrus’s as well. That discussion, however, could wait until the shock of this world was not quite as fresh. They would need time to adjust.

Gaster walked Sans back to the main facility as he wondered how long that would take.

 

\---

 

Once Gaster had a moment to himself, he trudged back to his office and practically collapsed behind his desk. Gaster leaned back in his chair, staring at the ceiling.

 _They were alive._ They were alive. All this time he’d thought their deaths had been on his hands, but they were okay. Well, apart from Sans’s health and Papyrus’s memories… and like Gaster’s cracked bones he had his doubts that those were things he could fix, though it certainly wouldn’t stop him from trying.

And with Sans’s help, perhaps he’d be able to advance some of his research. His soul studies had been developing slowly, and the DT operation had all but stalled once Alphys had refused to continue with the experiment. But perhaps now he could revitalize some of his old efforts.

Things might be looking up.

“Golly, what an exciting day!”

Gaster flinched at the voice, then sighed. Just when he had been in a good mood, too.

Don’t acknowledge it, he reminded himself. Acknowledging it only made things worse.

Gaster straightened up in his chair, then reached for the file he’d been going over before Sans and Papyrus had arrived.

“Two new skeletons, can you believe it?” the voice continued. “Gee whiz, I can’t remember the last time I saw another skeleton pop up. Besides you, of course.” It giggled. “Quite the coincidence, huh?”

Gaster ground his jaw, trying to focus on reading the text. He gestured for a pen, and one of his constructs retrieved one. He stared at the file, reading the same line several times.

“I wonder if they’re like you in other ways, too!” the voice mused, obnoxiously cheerful. “Do you suppose they have the same magic abilities?”

Gaster pushed the pen against the page, tracing out gibberish.

“Hm? No response? Oh well! I guess I’ll just have to find out on my own-”

“Leave Them Be,” Gaster snapped, disappointing himself by giving in. “They Don’t Have My Abilities.”

“Oh? You’re sure?”

“Yes,” Gaster said shortly, massaging the crack below his eye. In truth he wasn’t sure at all, but he thought Sans would have said something if he’d noticed the powers. Gaster had certainly discovered his immediately after arriving in the Underground.

It had been a disorienting experience.

“Hmm, sounds like you know a lot about them. You and the small one sure did talk for a long time!”

Gaster stiffened, wondering how much of their conversation had been overheard. He’d thought he’d secured his lab, but it was almost impossible to keep that weed out of anything.

“He’s Merely An Old Colleague,” Gaster said. “I Was Interviewing Him For A Position At The Lab.” The last thing he need was for it to become interested in Sans and Papyrus as well.

The thing giggled. “Tee hee! You and I both know you’re lying! Gosh, how funny. Are you trying to protect them? Maybe I should go ask them how they _really_ know you.”

Gaster dropped all pretenses. “If You So Much As Touch Them I Will End You. I’ve Done It Before And I’ll Do It Again.”

“Golly, you’re being so serious!” it giggled. “You must really care about them!”

Gaster didn’t bother replying.

“Do you think they care about you, too?” the voice continued. “Do you think they’d care about you if they knew what you’ve done?”

“They’d… They’d Understand,” Gaster said. But would they?

 _No_ , a voice whispered in his mind. _They can never know._

“If you say so!” the voice laughed. “Say, you like to experiment on things, right? We could make this an experiment, too! Test your theory. I’ll go tell them everything about you, and then-”

Gaster’s chair slammed back against the wall as he stood, a blaster materializing over his shoulder.

“ _You Will Leave Them Alone._ ”

But by the time the glow of his blaster illuminated the corner from which the voice had been coming, the only telltale sign of its presence was a small crack in the tiled floor.

 

 

**Notes for the Chapter:**

> Whoof, that was a long one. Sorry for all that exposition, but I hope it was at least interesting to read. Three chapters left (unless next chapter gets too long and I break it up into two chapters like I probably should have done with this one.)
> 
> Thanks for reading!
> 
> EDIT: Okay, so, next chapter definitely needs to be split into two. Sorry about that. This story will end with Chapter 17.


	14. Experiments

**Summary for the Chapter:**

> Gaster runs some tests with the assistance of Sans and Papyrus.
> 
> Man, I know I said this was going to be the third-to-last chapter, but it was getting so long that I just had to break it in two. I guess I'm really bad at predicting how long it takes to write this stuff, haha.   
> On the plus side, the next chapter should be done fairly soon.

Despite what he’d discussed with Gaster, Sans asked Papyrus to come back to the lab with him the next day. 

“it’s a medical device,” Sans explained to his brother as Gaster once more set up the machine. “it measures your health and stuff.” 

“I STILL DO NOT SEE WHY THAT NEEDS TO BE TESTED,” Papyrus said, sitting down regardless. “I AM IN EXCELLENT CONDITION!” 

“i don’t doubt it, bro,” Sans said.  _ But just to be safe… _

“Can You Form Your Soul?” Gaster asked. “It Might Take Some Concentration To-”

“LIKE THIS?” Papyrus asked, a heart forming in his chest. 

“Oh,” Gaster said. “Hm, Yes, Very Good.” Gaster held up the measuring wand. “Now You’ll Have To Move It Outside Your Ribcage, Which Might Be A Bit- Ah.” Papyrus’s soul floated out from between his ribs. “You Catch On Quickly.” 

“NYEH HEH HEH!” Papyrus laughed triumphantly. “OH COURSE I DO! I AM THE GREAT PAPYRUS, AFTER ALL.” 

“you are pretty great,” Sans agreed, though his attention was on Gaster and his machine. His nervousness mounted as Gaster reached out for the soul; it was silly, he knew, but he couldn’t help but worry. Sans held his breath as Gaster touched the dowel to Papyrus’s heart. 

Then released it in a sigh of relief as the screen populated. 

Gaster listed off the readings. “Health: 1950/1950. Magical Potential: 1500. Everything Here Seems Reasonable To Me.” 

_ Thank god, _ his health was high. Papyrus was okay. But his numbers were still lower than Gaster’s - especially his magic reserves. 

“why’s his magic so much lower than…”  _ mine  _ “...yours?” Sans asked. 

“Actually, It’s Rather High For A Typical Monster,” Gaster said. “The Vast Majority Don’t Break 1000. But Of Course, The Metrics Can Be Increased With Training, As Mine Have Been.” 

“so, yours are just higher because you’ve been here longer?” Sans asked. 

“More Or Less,” Gaster said, glancing away from Sans as he adjusted a few dials on his machine. Sans frowned, feeling there was something more to Gaster’s words, but he let the question go. There was still so much he had to learn about this world, after all. 

“ARE YOUR HANDS MAGICAL?” Papyrus asked, watching Gaster’s many sets of magical constructs assisting him with his work. 

“Hm?” Gaster looked up. “Oh, Yes, They Are. Most Monsters Can Form Physical Constructs Of Some Kind.” 

“UNDYNE MAKES SPEARS,” Papyrus said. “SHE SHOWED ME WHEN WE WERE SPARRING. THERE WERE… LOTS OF SPEARS.”

“Yes, Monsters Tend To Create Constructs With Which They Have Some Affinity,” Gaster said as he turned the machine off and began to pack it away. “It Took Me Some Time To Have Enough Precision To Form Simple Bones Into Hands, But They’ve Proven Themselves Quite Useful With-”

“I CAN ALSO MAKE BONES!” Papyrus declared, summoning a large bone before him and snatching it out of the air. Gaster gave a start, causing Sans to chuckle.

“Good Lord, You  _ Do _ Catch On Fast,” Gaster said. “Can You…” Gaster paused, rubbing at the crack on his skull in thought. 

“...what is it, doc?” Sans prompted. 

“Hm,” Gaster considered. “I Was Just Wondering If Papyrus Could Do Other Kinds of Magic As Well - Beyond Constructs,” he added. “Monsters With Higher Levels Of Magic Can Typically Display Unique… Abilities.” 

“is that so?” Sans said, wondering what that meant for himself - and Gaster. “and what about you, doc?” he asked. “do you have some kind of ‘unique ability?’”

“Yes,” Gaster admitted, removing his hand from his cracked skull. “However It Would Not Be Possible To Demonstrate. Papyrus?” he prompted again before Sans could ask him to elaborate. “Can You Think Of Anything Else?”

“WELL,” Papyrus considered. “THERE IS ONE OTHER THING.” He pointed his bone at Gaster, and there was a quiet  _ ping _ . 

“NYEH HEH HEH,” Papyrus laughed at Gaster’s shocked face. “YOU’RE BLUE NOW.” 

Gaster staggered and caught himself of the edge of his machine, nearly pulling it to the floor. “Good Lord.”

“woah, hey!” Sans jumped up to help. “you okay?” 

Gaster’s hand constructs waved Sans off as he straightened himself up with some effort, leaning heavily on the medical equipment. “Fascinating,” Gaster said, looking down at the blue that glowed through the front of his lab coat. “Artificial Gravity? This Is Very Impressive, Papyrus.”

Papyrus beamed. 

“An Imposed Field Of Microgravity,” Gaster continued to muse. “Quite Remarkable. I’ve Never Seen Spatial Abilities Like This Before. Papyrus, I’d Love To Run Some Tests To Learn More About The Potential Of These Powers...” He hesitated, trailing off as Sans gave him a pointed look and folded his arms. “...But Perhaps That Can Wait For Another Day,” Gaster quickly amended. “Thank You, Papyrus, You May Stop Now.” 

“NYEH HEH HEH HEH,” Papyrus laughed, banishing the magic. “YOU SHOULD HAVE SEEN YOUR FACE! IT WAS QUITE AMUSING!” With the magic gone Gaster straightened up, cracking his neck with a wince.

“i didn’t know you could do that, bro,” Sans said, turning to his brother. 

“I DISCOVERED IT YESTERDAY WHEN UNDYNE AND I WERE SPARRING,” Papyrus explained. “SHE WAS ALSO QUITE SURPRISED - AND A LITTLE UPSET, I THINK. SHE DID NOT LIKE GETTING KNOCKED DOWN. TRAINING GOT A LITTLE… INTENSE AFTER THAT.”

Gaster chuckled. “I Can Imagine. Undyne Isn’t Exactly One To Turn Down A Challenge - Or Lose A Fight, For That Matter.”

Sans wasn’t sure how he felt about his brother hanging around this Undyne character. From the brief interaction he’d had with her, she’d seemed a bit… blunt, at best.

“DID YOU KNOW SHE’S THE CAPTAIN OF THE ROYAL GUARD?” Papyrus was saying. “SHE SAID IT IS NOT EASY TO MAKE IT INTO THE ROYAL GUARD. BUT IT SOUNDS QUITE EXCITING! YOU HAVE TO BE NOBLE, AND CHIVALROUS, AND STRONG, AND WEAR ARMOR - SANS!” he exclaimed. “DO YOU THINK I COULD BE IN THE ROYAL GUARD?” 

Sans didn’t know why he was surprised - Papyrus had been obsessed with knights every since they were kids. “a guard, huh?” he considered. “well, if that’s what you want to do, i don’t think there’s anything that could stop you.” Even so, the conversation made him a little uneasy. He and Papyrus would still be going home - eventually. Gaster probably had done a ton of research on how to return to their reality, and Sans didn’t want Papyrus getting too invested in things here in the meantime. Maybe he shouldn’t wait for his brother’s memories to return after all. It wouldn’t be an easy conversation, but it might be better to have sooner rather than later...

Papyrus was swinging around the bone he had constructed, apparently in reenactment of his and Undyne’s sparring match the previous day. “AND THEN SHE STABBED LIKE THIS!” he said, Gaster watching impassively. Papyrus jumped to his feet. “AND I SPUN LIKE THIS!” He twirled, smashing his bone into the side of Gaster’s machine and causing the medical device to crash to the ground in a sparking mess. 

“OH NO!” Papyrus cried. “I AM SO SORRY! I DID NOT MEAN TO!”

“Damn,” Gaster sighed, looking down at the broken machine. “Don’t Think I’ll Be Able To Fix That.” 

“I AM SORRY!” Papyrus repeated. “I- I WILL FIND A WAY TO FIX IT! THERE MUST CERTAINLY BE A WAY-”

Gaster wasn’t listening. The scientist frowned, looking at the machine thoughtfully, before seeming to make a decision. He waved a hand and a purple light briefly illuminated from beneath his lab coat. At the same time Gaster’s hand constructs glowed brighter, and a sickening wrench pulled at Sans’s gut. The world seemed to tip, Sans’s head spinning-

And then everything snapped back to normal as if nothing had transpired.

Sans gripped the side of Papyrus’s chair for support, disoriented and nauseous. 

“-SAID  IT IS NOT EASY TO MAKE IT INTO THE ROYAL GUARD,” Papryus was saying. “BUT IT SOUNDS QUITE EXCITING! YOU HAVE TO BE NOBLE, AND CHIVALROUS, AND STRONG, AND WEAR ARMOR - SANS!” he exclaimed. “DO YOU THINK I COULD BE IN THE ROYAL GUARD?” 

“uh,” Sans stammered, looking around. Hadn’t Papyrus already asked him this? And he was sitting back down in his chair, too. As Sans tried to gather his wits, he noticed Gaster packing up the medical machine - the medical machine that was still upright and very much unbroken. Casually, Gaster rolled the device a few extra paces away from Papyrus. 

“what?” Sans said, having already forgotten what his brother had asked him. 

“SANS” Papyrus prompted. “ARE YOU ALRIGHT?”

“i- i don’t know,” Sans admitted. “what just happened? why’re you guys… ugh.” Sans let go of Papyrus’s chair to rub his head. “i’m going crazy.” 

Gaster glanced over at Sans curiously. “What Is It Sans?”

Sans shook his head. “nothing, i guess. i just. for a moment i thought papyrus broke your machine, and then… never mind, it’s stupid.” Sans gave a weary chuckle. “guess i’m just  _ bone  _ tired.”

But Gaster was looking at Sans in awe. “You Remember?” he asked, his face lighting up with excitement. “You’re Cognizant Of Time Jumps?” 

“time... jump...?” Sans blinked. It took a moment for the words to sink in. “no way.” 

“Yes!” Gaster said, his hand constructs jittering about excitedly. “Yes Way! Very Way!  _ Stars _ , You’re Only The Second Monster I’ve Encountered That’s Been Able To Remember The Jumps!” Gaster grabbed Sans by his shoulders, and for a moment Sans thought he was either about to be tossed into the air or pulled into a hug. Instead, Gaster just shook him giddily. “This Is Amazing! It Must Have To Do With Your Own Magical-” Gaster cut himself off mid-sentence, as if suddenly worried of voicing his thoughts aloud. He frowned briefly, but it was quickly overtaken by his mirth once more. Gaster let him go, returning to pacing frantically. 

“was that you, doc?” Sans asked, his mind still spinning. “did you do that?”

“I HAVE NO IDEA WHAT’S GOING ON,” Papyrus also took the opportunity to speak up. 

Gaster ignored him. “Yes, It’s My Innate Magical Ability. I Have Slight Temporal Powers Which Allow Me To Travel Back In Time - Only For A Handful Of Seconds, However.” He patted the medical scanner. “Enough To Fix Small Mistakes.” 

“holy shit, doc,” Sans said, flinching as his brother muttered, ‘Language.’ “that’s amazing!”

Gaster shook his head. “Perhaps Not Nearly As Amazing As Whatever You Might Be Capable Of. Don’t You See, Sans? I, With Temporal Powers, Your Brother, With Spatial Ones - There’s A Clear Link Between The Nature Of Our Abilities.” 

“spacetime,” Sans said, his eyes widening. Exactly the same natural properties they’d been trying to bend to their will when they’d gone through the time machine in the first place. In becoming monsters, they’d gained some small control over the very nature of existence… Sans wasn’t sure if he should feel powerful or terrified. 

“what does this mean?” Sans asked. “can... can we harness it?” Could they use it to go home?

“I Don’t Know.” Gaster’s eyes flashed purple with excitement. “But I Intend To Find Out.” 

 

\---

 

Sans and Gaster spent the next few days exploring Sans’s powers. They’d discovered he shared his brother’s ability to make bone constructs and gravity fields easily enough; all it had taken was him bothering to try. Even so, Gaster believed there were more to his abilities than met the eye.

“i dunno, g, maybe that’s it,” Sans said, spinning a bone across their makeshift testing grounds with a lazy twirl of his fingers. The room was adjacent to Gaster’s lab, and had largely been cleared out to minimize the destruction of Core property should their experiments not go as planned. “makes sense papyrus and i share the same powers, being brothers and all.” 

“I Would Be Inclined To Agree Were It Not For Your Magical Potential,” Gaster said. “That, Combined With Your Ability To Perceive My Time Manipulation, Makes Me Believe There Is Something We Are Still Missing.”

Sans shrugged. “i dunno, i feel like we’re wasting our time here… we haven’t discovered anything new in two days, and we could be working on some of your other projects right now instead.” Gaster had discussed with Sans a few experiments that he currently had underway; most of them involved powering mechanical devices off of magic and operating magical devices remotely, but a few delved into more theoretical fields, such as the nature of souls and magic. Sans thought it was a little odd that none of Gaster’s current projects involved spacetime travel, though he’d yet to talk to Gaster about why that was. Regardless, it was what Sans planned on studying once he’d settled in and had a place to work.

“This Is Directly Related To Our Research, Sans,” Gaster said. “If We Want To Be Able To Use These Powers To Further Our Objectives, Then We Must Know The Extent Of Them.” Gaster rubbed his jaw thoughtfully. “Perhaps We Are Approaching This The Wrong Way.”

“how’s that?” Sans asked. “we’ve tried just about every variety of magic you can think of.” Sans tacked them off on his fingers. “fire magic, temporal magic, summoning magic, sensory magic, basically every sort of construct that exists…” Sans shrugged. “seems like we’ve run out of options.”

Gaster shook his head. “I Disagree. Those Are All Types Of Magic That I Have Personally Witnessed. However It Is Quite Possible That There Are Other Abilities That I’ve Yet To Discover.” 

“that leaves us infinite possibilities,” Sans pointed out. “how could we possibly test for all potentially possible abilities?”

“As I Said, I Believe We Are Approaching This The Wrong Way.” Gaster’s eyes glowed purple, and a canine skull flashed into existence before him. “We Need To See How Your Magic Responds Instinctively.” 

“woah,” Sans said, his bone constructs fizzling out at his surprise. The skull was almost bigger than Sans, and had glowing eyes of its own which blinked with a disturbingly life-like sentience. “what kind of magic is that?” 

“It’s Not, Exactly,” Gaster said. “I Created It A Few Years Ago After Reading Into Some Research On Soulless Monsters - Though It’s More Magic Than Monster, And More Machine Than Magic. It’s Tethered To My Soul So I May Summon It At Will.”

“damn,” Sans said. “that’s pretty… intense. what’s it for?”

“It’s A Weapon, Sans,” Gaster said. The jaws of the skull opened, and a white light began to glow within its maw. “I Can Channel My Magic Through The Blaster In Order To Discharge Concentrated Beams Of Energy. I Think It Will Be Useful In Encouraging Your Powers To Be Expressed.” 

Sans laughed nervously, eyeing the blaster. “very funny, doc. what’s it really for?”

“Remember, Sans, Intent Is The Key To Magic,” Gaster said, ignoring Sans's question. The light in the blaster’s mouth was getting brighter, and Sans was no longer smiling. “So Long As I Do Not Wish You To Get Hurt, The Attack Should Be Harmless.”

“h-hey, hold on a sec, doc,” Sans said, taking a step back. Holy shit, was he really serious about this?

"You Have Nothing To Fear," Gaster repeated. "This Is Merely To Test How Your Magic Responds On Instinct. Besides," he added as an afterthought. "Even If I Do Underestimate My The Strength Of My Magic, I Can Always Perform A Quick Time Jump Should You Become Injured."

Sans felt his bones go cold. "injured?" he croaked. He only had one health point. Did Gaster mean injured, or dead? 

“Ready, Sans?”

“ _ What? _ ” Sans cried in panic. “No! no, doc, i’m not freakin’-”

Gaster raised a hand, and the blaster fired. 

Sans felt his heart jump in his chest. He didn’t have time to think or react - the glow of the blast filled his vision, searing towards him, and it was all he could do to gasp as the energy rushed through him. 

Sans took a step back, his shoulders thumping into a wall. The light that had filled his vision was now far to his left, but Sans was more focused on catching his breath. He was… alive?

“Sans? Sans? What… Oh.” There was a pause. “Amazing!” Gaster cried, his voice now coming from the other side of the room. “I Must Say, I Was Not Expecting Results To Be So Immediate… Sans? Are You Alright?”

Sans looked at Gaster, trying to understand what had happened. How had Gaster gotten all the way over there?

“h-holy shit, g,” Sans said, clutching at his chest with one hand. “what the hell was that?”

“You Teleported!” Gaster exclaimed. “At Least, I Assume You Teleported. That Wasn’t Extreme Speed, Was It? Or A Temporal Bubble, I Suppose?”

“no, doc, i mean  _ what the hell was that _ ?” Sans said, starting to get angry. “you shot me! what the fuck!” 

“As I Explained, Sans, It Was Completely Harmless-”

“you nearly gave me a heart attack!”

“I Don’t Believe That’s Physiologically Possible.” 

“you asshole!” Sans summoned a bone and threw it at Gaster. Gaster didn’t bother dodging, and the bone bounced harmlessly off his shoulder. 

“I Probably Deserve That.”

“ya think?” Sans huffed, glaring at Gaster. “seriously, doc, that was messed up.”

“I Apologize,” Gaster said, though Sans was unconvinced of his sincerity. “But You Can’t Deny That My Method Produced Results.” 

Sans muttered something about Gaster’s methods under his breath and delivered a heartfelt kick to the wall, no doubt injuring his foot more than concrete. Still, it helped release some of his frustration he would much rather take out on the scientist. Sans glared at Gaster, then took a moment to look around the room.

As much as he hated to admit it, Gaster was right. Either the room had flipped 180 degrees, or he had teleported behind Gaster when the scientist had attacked. Sans suddenly recalled a similar moment, when he’d been in the woods with Papyrus. There had been a moment when he’d been at the top of the hill looking down at his brother and the rabbit monster, and then the next instant he’d been at Papyrus’s side. At the time he’d thought he’d blacked out or was having memory problems, like his brother, but now…

Well, there was only one way to be sure. 

Sans picked a point on the other side of the room. If it worked like the gravity and magic constructs then all he had to do was will himself there. Sans lifted a foot, took a step, and felt his soul glow with warmth.

Unlike Gaster’s time manipulation, which left Sans a little disoriented after each jump, the teleportation was seamless. It was as simple as stepping through a doorway: one moment Gaster had been on the other side of the room, and the next moment Sans was standing next to him. 

Gaster jumped at the sudden appearance of the smaller skeleton, which Sans found satisfying. He hadn’t expected it to be that easy. But damn if this wouldn’t make Gaster smug.

“huh,” Sans grunted, stuffing his hands into his pockets. “so. teleportation powers, then.”

“It Appears So,” Gaster said.

Sans scuffed his foot on the ground. “well. i guess teleporation powers are pretty cool.” In spite of himself, a smile slowly crept back onto his face.

“Sans,” Gaster said, completely serious. “Teleportation Powers Are  _ Very  _ Cool.” 

Sans chuckled, then shook his head with a sigh. “i can’t stay mad at you, gaster, even if I  _ want  _ to be. but to make up for it, you’ve got to promise me two things.”

“Of Course, Sans,” Gaster said, giving him an inquisitive look. “What Is It?”

“first,” Sans said, raising a finger, “you never pull shit like that on me again.”

Gaster was already nodding. “Of Course. I Only Thought It Was The Right Thing To Do Given The Extenuating Circumstance - But I See It Caused You Some Distress. It Won’t Happen Again.” 

Sans had some choice words about how “extenuating” the circumstance was, but he let it be. “fine. second,” he said, pointing his finger at the blaster still hovering beside Gaster. “i want one of those.” 

Gaster looked at the weapon in surprise, then began to laugh. 

“Sans,” Gaster said. “You Can Have As Many Of These Blasters As You Want.”


	15. The Extractor

**Summary for the Chapter:**

> In which Sans goes looking for answers and finds more than he bargained for.

**Notes for the Chapter:**

> Man, I thought I was going to get this chapter out early, too. Instead it grew to over 6000 words. Enjoy!
> 
> I'm not really sure how much warning is necessary to give (I'm still kind of new at this) so I'll just say: mind the tags.

 

 

Days turned into weeks, and those into months. Despite the fact that Sans was still adjusting to the Underground, things began to fall into a routine to the point where everything began to feel… _normal_.

Gaster had arranged housing for them in Hotlands, though Papyrus was eyeing a lot back in Snowdin. Sans spent his days at the Core while Papyrus was still pining after a position on the royal guard. He’d managed to convince Undyne to train him - even her stubbornness was no match for Papyrus’s resilience - and he often spent his time sparring or cooking while Sans was at the lab. At the end of each day Papryus always had some story to tell or a new recipe for his brother to try; Sans had never seen Papyrus so happy.

And Sans was happy, too, if he cared to admit it. Working with Gaster was never a dull moment. Sans was always running some new test or experimenting with things he’d never even believed were possible back home. No two days were the same, and he always left exhausted in the evening and excited to return to work each morning. It was almost like the days when he and Gaster had worked together before Papyrus had been caught in the accident - only now they had a far greater budget.

Well, that wasn’t the only thing that was different. Occasionally Sans found himself noting changes in Gaster’s behavior. The scientist had always been blunt, distracted, and empathically inept, but sometimes Sans caught notes of indifference - even callousness - that hadn’t been there before. The day Gaster had startled Sans into discovering his teleporation ability was the most obvious example of this shift, but certainly not the last. Sans suspected it had to do with the years he’d spent in the Underground, a subject of which he rarely spoke, and when he did, only sparingly. There were things Sans knew the doctor was keeping from him, but then again Sans kept his own secrets, and could hardly blame Gaster for that.

After discovering Gaster had scrapped all work on the time machine, for instance, Sans decided to rekindle the research himself. He worked on it in his spare time and whenever Gaster wasn’t around to notice. While he didn’t think the scientist would stop him, Sans did note that trying to talk about the time machine was a sore subject for Gaster, and any conversations related to it often left him irritated. Maybe he was ashamed it hadn’t worked as intended, or maybe he believed he didn’t need it anymore now that he had temporal abilities of his own. Whatever the reason, Sans hadn’t been able to weasel it out of him.

 

Occasionally, on the bad days, the laboratory would shake from tremors in the Core. Those days their research was abandoned, and Gaster was forced to spend his time in the depths of the facility performing maintenance and supervising the Core until he could be certain that all was stable once more. Not many monsters could weather the lower levels of the laboratory for long; the magma that powered the Core made the levels sweltering, and rare bursts of volcanic activity threatened to sear through the metal walls and magical barriers that protected the facility. Sans had offered to help Gaster - the scientist sometimes had to spend over 24 hours at the lower consoles, keeping watch for any crack in their defenses - but Gaster had refused on the grounds that it was too dangerous for a monster of such low health. His refusal stung, but Sans understood. On the bright side, it allowed Sans more time to work on his own projects.

It was on one such day that Sans decided to search for Gaster’s old notes on the time machine. It wasn’t _snooping_ , really, just… proactive research.

The archives turned up nothing, however. Not even documentation of Gaster’s own abilities - though Sans supposed that too surprising, given he was the only one that was aware of the powers in the first place. He tried Gaster’s lab next, riffling through the notes the doctor left scattered throughout desks and filing cabinets, but it proved equally fruitless. Sans tapped at his teeth in thought, then teleported to the lab’s south wing.

Given the Core’s extensive and labyrinthine design, there were areas of the facility Sans still hadn’t explored. One such place was the south wing, an old section of the lab that had been closed off about two years before. Alphys had mentioned it to Sans once, though she’d staunchly refused to discuss any of experiments that had gone on there when it had been operational. When he’d tried to bring it up with Gaster the scientist had grown agitated and quickly changed the subject - if the research on spacetime travel was anywhere, it was there.

The passageway to the wing was blocked off, but Sans had a shortcut.

Teleporting through the wall, he found himself in nearly complete darkness. A few cracks let light in from beneath the door and around the hinges, but otherwise he was blind. That was an easy enough problem to fix; Sans summoned a blaster and let a bit of his magic through the bond, illuminating the area with a faintly blue glow. Using the blaster as a glorified torch wasn’t the best use of the weapon, and he suspected that if the blaster were capable of thought it would be offended. Keeping the blaster lit was also a small drain on Sans’s magic reserves, but he didn't concern himself much over that; if his experiments with Gaster were any indication, it would take a lot more than one blaster to sap his energy.

The blaster guiding his way, Sans began to walk into the deadened depths of the Core. He peered through the doorways he passed - most of them simple offices and storage rooms - but he suspected he wouldn’t find what he was looking for until he was much deeper into the wing. The labs were often removed from the day-to-day office work in an effort to mitigate the danger of collateral damage from any experiments gone wrong, though Gaster’s office was never far from where those experiments took place. Sans didn’t imagine it would be difficult to find: whatever room was closest to the most amount of exotic equipment was likely to be his. If it existed at all, Sans expected to have the research he was looking for within the hour. And hey, even if he were wrong about Gaster’s work on timetravel, he couldn’t pass up the opportunity to poke through the scientist’s old notes.

Like the rest of the Core, the passages Sans passed through wound about in an almost senseless pattern. He might have worried about getting lost in such a place if he weren’t able to just take a shortcut home. The further he traveled the quieter it got, until eventually the quaking of the Core became only a distant rumble. The air, too, was muted. Heavy, almost, as if resistant to the wisps of stirred currents Sans left in his wake. His footsteps didn’t seem to echo quite as loudly as they should, and the hum of his blaster faded until it was little more than background static. Sans didn’t consider himself the type to become easily flustered, but the disquiet of the place left him feeling… uncomfortable. He began to wonder why the wing had been closed in the first place.

The passage opened into a wide room. The light of his blaster left the furthest corners in darkness, so Sans fed more magic into his blaster to up the brightness. Even then the room still seemed dark - perhaps it was the metal walls that made it feel so oppressive.

Or maybe it was the rows of empty beds.

“...the hell?” Sans murmured, passing the cots by. It didn’t seem like they’d been used in some time - but why were they even here? Had the south wing been used as an infirmary of some kind? And if that were the case, why had they stopped using it? Uneasily, Sans continued on.

The path branched from there, Sans picking a corridor arbitrarily. This led to another series of abandoned rooms and offices - one of which, Sans was sure, had to be Gaster’s. Sans glanced into a couple of these, stopping only when he came upon another wide room. Hoping this area would appear more lab-like than the last, (and that, by extension, Gaster’s office would be somewhere nearby,) Sans sent his blasters ahead to search the area.

The room wasn’t as big as the last, and felt even smaller from the large piece of equipment that filled the northern half. Sans mistook it for a skull at first, though the way his blasters glinted off the surface indicated it was only styled after one: the machine stood at least two monsters tall and equally as wide. Large coils snaked away from the skull, worming into the walls and floor of the lab. It was eerily reminiscent of the blasters Gaster had designed, though where light shined from the eye sockets of Sans’s weapons, the machine in this room remained quietly dark and dormant.

Lights danced around and through the hollow structure as Sans sent his blaster to investigate it, casting strange shadows about the surrounding surfaces. Swaths of black and white rose and fell with the passing of the blaster, some moving with unsettlingly lifelike flickers and into unsettlingly lifelike shapes. As the blaster circled the machine, one shadow, however, failed to yield to the passing light.

The shape stayed solid before the weapon’s light, though even in its solidness it remain indistinct. Its form wavered, sagged, reformed; a segment of the shadow separated from the mass, reaching out to touch the mechanical skull. Sans gave a start as he realized the shape was that of some other monster that had been lurking in the lab’s darkness.

“h-hey,” Sans said, finding his voice. The figure didn’t respond. “hey,” Sans tried again, a little louder. “didn’t know there was anyone else down here. what are you…” His voice hitched as the thing tipped its face towards him.

“...gaster?”

The thing before the machine was and wasn’t Gaster. It had his form, mostly, but it never stayed stable for long, constantly melting and shifting and reforming back into its almost-Gasterness. A smile cut like a wound across its face, uneven and far too wide. The thing was unsettling on an instinctive level, something that came from its essence more than its appearance. Looking at it was like trying to see light in a void, like pressing two like-poles of a magnet together. It did and didn’t have a soul, as it did and didn’t exist.

The thing that was and wasn’t Gaster spoke, and the words tumbled out just beneath the skin of reality. They tripped over each other, the sound out of focus and not quite tuned to the frequency of this existence. The words were made more of intention than comprehension - but intent was the true language of this world.

_Curiosity. Grief. Amusement. Pain. Hatred._

Sans took a step back, every alarm bell in his head ringing. “s-stay back!”

Its head titled impossibly far and another flurry of words met his demand, all susurration and conflicting impressions. Out of disquiet as much as a desire to get a better look at the thing before him, Sans summoned a second blaster and pointed its maw at the figure. As the light flitted over the mechanical skull, shadows once more flickered around the room. The figure removed its hand from the machine, instead raising it towards Sans, and there was another spark of intentions that accompanied the movement. Before Sans could grasp the purpose of the gesture, however, a shadow passed over the figure and it vanished.

“what the…” Sans’s head whipped around, trying to figure out where it had gone. His blasters followed his motion, briefly sending a dizzying pattern of lights around the room before he stilled them. Each new jump of a shadow sent another chill up his spine, but by the time everything came to rest once more it was apparent he was alone.

Sans took a moment to try to asses what had just happened. One second it seemed like Gaster had been standing there, and then next he was gone. Sans hadn’t detected any time jumps, so that couldn’t have been the cause. But while the creature before the machine had _looked_ like some warped version of Gaster, it certainly hadn’t _felt_ like him. In fact, now that he thought about it, he wasn’t even sure he’d been able to sense its soul.

So had there even been anything in the room with him at all? The few brief moments the being had been present felt surreal, and the creature’s form had been as indistinct and versatile as the shadows themselves - perhaps his mind had just been playing a trick on him. Perhaps he had just imagined a familiar face into a series of random patterns. Perhaps his ears, strained from so much silence, had imagined words into the distant sonance of the Core. Perhaps… Perhaps.

Sans teleported before the machine, pulling his blasters closer around him. The nose of the skull stood almost as tall as Sans himself, and up close he could see the seams in the metal where the skull could split open. The device was covered in a film of dust, beneath which the metal appeared weathered from use. With a sinking feeling in his chest Sans could also see a glint of light where his blasters reflected off a cleared patch of metal - precisely where the figure had touched the skull. Sans lifted his hand and placed it over the top of the mark; his bones were smaller, but it was definitely the handprint of a skeleton.

So he hadn’t imagined it after all.

But if that thing _had_ been Gaster - and Sans still wasn’t even sure about that - where had it gone? Sans glanced around the room superstitiously, but he still appeared to be alone. Sans didn’t like this. Maybe coming down here at been a mistake.

Beneath his hand, a subtle warmth prickled at his fingers. Absorbed in his thoughts, Sans didn’t notice until the warmth grew into a heat, and pulsed gently against his hand. Sans looked down in surprise, feeling a second pulse of energy. Lifting his hand to examining the surface of the machine, nothing appeared to have changed. Sans carefully placed his hand back down on the skull and detected another ping of magic, stronger this time. It was a prompt - a call waiting for a response. A magical command line and blinking cursor, waiting for user input.

Sans hadn’t forgotten about the Gaster-like being that had just been standing where he stood now, but his curiosity was painfully hard to ignore. He wasn’t sure what this machine did, or if it had anything to do with spacetime travel, but he was certain it was designed by Gaster. Against better judgement, Sans leaked some of his magic into the machine.

His magic zipped away, drawn through a series of circuits that suffused the skull in a web-like array of magic. As his magic flowed through the device Sans was able to detect hints of functionality, indicating points where more power should be fed, or which flags should be set to enable what functions of the machine. The skull began to hum, and before he could stop it the circuits pulled at him, sapping a small burst of magic out through his hand.

“hey,” Sans objected, quickly taking a step back. Even after he’d broken contact with the machine, however, he could still feel his magic flowing through it. The machine had pulled just enough energy to turn itself on, though it required further instructions before any of its functionality could be executed. In a crude way, it was similar to how Sans’s blasters were tethered to his magic. Without him there to provide power and instructions they were little more than scrap junk. In this case, a very big and menacing piece of scrap junk.

Sans thought he could puzzle out what it was for. There were an array of commands it could accept, some of which were simple to understand - opening and closing the machine, for instance - and others which took more thought. From what he could make out an object was supposed to be placed inside the machine - like a battery - which would then be used to draw power to other parts of the device. The tubes that snaked away into the walls and floor were to absorb and direct most of this power - though for what purpose Sans couldn’t decipher. For that matter, he wasn’t even sure why the battery step of the process was even necessary. Since the machine ran on magic, couldn’t that energy source be extracted directly? There was something he was missing, though without knowing more about the machine’s purpose it would be difficult to say.

Sans was still trying to figure out this last puzzle when a quiet giggle echoed around the room.

Sans spun around, his blasters mirroring his movement.

“who’s there?”

Sans watched tensely as the shadows dipped and swelled with his blasters’ light, but no one else appeared to be in the room.

Sans stood still, waiting and listening for a minute longer. His blasters’ lights wavered in the silence.

“hello?” he tried again. But there was no response.

Sans thought the sound had come from the hallway leading into this room, but he couldn’t be sure. Giving the skull one last glance, Sans decided he needed to move on. If there was someone else hanging around the lab, he needed to be on guard - and he needed to focus on what he had come down here to look for in the first place. The extracting machine would have to wait. Mentally, Sans flipped the appropriate magical switch to power the device down, and the hum of the machine slowly, reluctantly, faded away. With that taken care of, he retraced his steps to the hallway.

The first door to his left was cracked open. Sans couldn’t remember if it had been that way when he’d passed by before, but with a now heightened and healthy dose of anxiety, he intended to be thorough regardless.

The office was filled with paperwork. It covered the desk, the floor, the filing cabinets; stacks of folders were spilled across the floor and hastily shoved into drawers. It appeared the mess hadn’t been straightened in some time, and the occasional tremors of the Core certainly hadn’t done anything to help. Despite the previous disconcerting discoveries of Sans’s exploration, he now found himself smiling.

“gaster, you slob,” Sans smirked, ignoring the hypocrisy of his statement. Only one scientist he knew left notes scattered about every available surface. Sans picked up the nearest document, recognizing the nearly-illegible handwriting immediately.

“guess this is it, then,” Sans said, sitting heavily in Gaster’s office chair with small puff of dust. He sent one more cautious glance around the office before he began to skim the first paper he’d picked up; despite the trepidation he was beginning to feel for being down here alone, he had to start sorting through the material somewhere, and there was a lost of material to sort through.

To his surprise, however, the first paper he’d grabbed contained references to a few formulas he recognized. Sans sat up, leaning over the desk to grab the stack the paper had come from. Leafing through the pages, he quickly realized that they were all related to Gaster’s time travel research. There was no way Sans was that lucky - standing back up, Sans began to pull pages from elsewhere on Gaster’s desk: page after page, without fail, each documented Gaster’s research, tests, and designs for his spacetime machine. There were even blueprints - highly detailed blueprints - for a machine a fraction of the size of the one he’d built before. This one didn’t need a warehouse; a small room would be sufficient to house it, if Sans was reading the schematics right. Everything here was far more refined than the formulas he and Gaster had used before - it must have taken years to get this far.

“so why’d you stop, g?” Sans mumbled. Why wouldn’t he talk about it now?

It was faint, but the lab was silent, so the sound was unmistakable: a quiet giggle echoed through the room.

Sans swore as he jumped, knocking a stack of documents off the desk into a flurry of papers. His blasters instinctively snapped to the sound, his gaze following only a moment later. There was a door in the back of Gaster’s office, one Sans had initially written off as storage space.

“who the fuck’s there?” Sans demanded, his heart beating fast in his chest. If he’d thought he’d imagined it before, he was certain he hadn’t now. Too many creepy things had happened in too close succession; he was done playing this game.

The office remained quiet as Sans took another step forward and tried the handle. The door swung inwards, its hinges protesting with prolonged screeches, but nothing stirred within.

“i _know_ someone’s here,” Sans said, hoping his heightened nerves made him sound more intimidating than scared. “now’s your last chance to come out... if you don’t want to have a bad time.” Sans waited a moment, and when the silence persisted he sent his blasters through, sweeping their lights through the room. When nothing stirred, he followed after.

It was bigger than he had expected, and definitely not a storage space. At least, not by any conventional standards. There were more documents, certainly, but there was also more equipment - and a large shrouded object that, despite only taking up a corner of the room, seemed to loom over the small space.

Before approaching the covered machine - one whose function he strongly suspected he already knew - he paused to take a second glance around the room. Once again the source of the laughter remained a mystery. Something was screwing with him, and he didn’t like it one bit. Sans made a decision then: he was going to grab as much of the research material as his arms could carry, and teleport right the fuck out of this hellhole of a lab.

...Just as soon as he finished investigating what was beneath the shroud.

Crossing the room, Sans pulled the sheet away from the covered object. It slid off smoothly, as if waiting for Sans to expose it. Sans sighed, almost unsurprised by what he found.

The time machine glinted from his blasters’ light, shiny and new as if it had never been used. In fact, Sans suspected that was likely the case; next to the machine was a monitor and recording device, both of which appeared to be far more weathered. Sans poked around the machine first, trying to see if it would open. The capsule appeared to be able to fit one occupant, and countless switches and knobs filled the interior. Touching it as he had the skull-like device outside, he was quick to discover that the machine was powered off of conventional electronics rather than magical energy. Presumably this was so it could be operated in other realities where magic didn’t exist, but unfortunately it left Sans at a dead end as to how it could be operated; he suspected, at least, the notes in Gaster’s office would detail the settings needed to make the machine work. The realization hit him all at once, and his soul lurched in excitement. With this, they would all be able to go home.

_So why had Gaster hidden it?_

Sans looked over at the recording device. The scientist was meticulous in his documentation - perhaps there would be answers in the videos he had made.

Several cassettes were lined in a rack beneath the monitor, all of which were labelled with a date, and most of which were labeled with brief descriptions. Sans wondered at the ones without descriptions, if Gaster had been too busy to write a summary for these, or if there were some other reason the field had been left blank.

The cassettes appeared to be sorted into categories by abbreviations, which, curiously enough, appeared to flow chronologically. The first set of tapes was labeled “DT,” the second “Ext.” and the third “ST.” Sans didn’t recognize the first two abbreviations, but suspect the last stood for “spacetime.” He decided it would be best to start there and move back.

Of course, that meant spending more time here.

There were too many tapes to take all at once - especially with the papers he intended to take with him as well. On top of that he doubted he’d be able to play back the cassettes without the devices that were set up here, and it would be cumbersome to disassemble and reassemble the setup that was being used to run the old hardware. Sans reluctantly resigned himself to the fact that he’d have to watch them here; perhaps he’d start with just a couple of the highlights to get an idea as to what Gaster had been recording, and then come back some other time to delve into more of the details.

Sans picked out the cassette with the most recent date (roughly two years prior) with the simple description “End.” Hoping it would contain some reasoning for Gaster’s abandonment of the project, he put the tape into the player and turned on the monitor. As he pushed the play button he turned one of his blasters on the door that led back into the office (just to be safe,) and reclined against the opposite counter to watch. The room flashed white and filled with static, causing Sans to squint after so much time in the dark.

After a moment the static flashed away, replaced with an image of Gaster at his desk. The scientist appeared haggard, his lab coat wrinkled and glasses askew. His eyes were unfocused and staring somewhere off camera. A few minutes passed without anything happening, and Sans was about to fast-forward when Gaster finally began to speak.

“It’s Done,” he said, lowering his gaze. “I’ve Finished It. Run Every Test. Double Checked Every Equation. Examined Every Figure. And It Should Work. I… I’m Almost _Certain_ Of It. Yet Still I Hesitate.” Gaster rubbed at the crack above his eye. “I Am A Coward, I Think. Selfish and Weak. Despite Everything I’ve Promised And Worked Towards, I Am Unable To Activate The Time Machine When It Matters Most. Would I Ever Have Activated It Back In My Universe Had Sans Not Done So First? Back Then I Certainly _Thought_ I Intended To Use It, But Now I Wonder…” Gaster’s eyes slid towards the camera, which he stared at for another long minute. Eventually he let out a pained sigh. “I’m Sorry. I Wish I Was Better Than This, But I Am Not Brave Enough To Use It. I’m Ending The Research. Ending… _All_ Of This. I Wish I’d Never Begun It In The First Place, But It Is Too Late For That Now. I Chose To Live With My Sins.”

The video ended.

Sans continued to watch the static, not knowing what to think. Gaster had been afraid to use the machine, that much was clear. But what sins was he talking about? And why was he so afraid to use the device if he was so certain it would work? The video created more questions for Sans than it had answered. After fast-forwarding the cassette to see if there were any more material, Sans removed it from the player and returned to the shelf to pick out another. Perhaps one of the earlier videos would offer some explanation. Selecting the last video from the “Ext.” set (this one did not have any description) he put it in the player and once more sat back to see what Gaster had to say. This time, however, the video displayed a different scene.

A coldness traced up Sans’s spine as the camera focused on a room that was all too familiar. Gaster was standing before a large skull-like machine, using three of his hand constructs to carry and make notes on a clipboard. Though the room was brightly lit the scene was disturbingly reminiscent to Sans, and he couldn’t help but recall the figure he’d seen standing before the derelict machine only a handful of minutes before.

“Test Seventeen,” Gaster was saying. “Subject Is Unresponsive, Which Might Assist In Reducing The Stress Of The Extractor’s Effects.” His gaze was on the skull, which was in the process of hissing closed. There was something inside of it, some hint at a form just beyond those darkened eye sockets, but Sans couldn’t make it out. “Test Sixteen Experienced Limited Success; With A Prolonged Duration And Increased Flow Rate, I Expect To See A Higher Yield In Extraction Of The Essence.” Gaster’s hand constructs glowed brighter as he accessed his magic; a moment later, the hum of the machine could be heard over the camera. Veins of indigo light traced over the skull, spiraling down into the eyes and depths of the machine. The whine of the device grew louder until it almost overpowered Gaster’s voice. As the lines of magic spread across the machine a tremor passed through its cables, as if a vacuum had just pulled the tubes taught. A moment later the ducts began to glow a faint yellow, and Gaster’s hands began to frantically scribble down notes.

“Stage One Successfully Executed,” Gaster said, his voice barely audible over the hum of the machine. “Interface With The Soul Complete. Initiating Stage Two.”

Sans frowned. Soul? What did he mean by that?

The yellow glow in the machine’s cables grew brighter. Some of the light began to leak from the eye sockets of the skull as well, slowly illuminating the machine from within. A change began to occur within the extractor’s cables, the golden light condensing into a more solid shape. Slowly, the light began to trickle through the ducts, flowing down and away from the machine like a viscous fluid.

“Extraction Initiated!” Gaster declared, practically shouting over the mechanical whine of the machine. “Begin Timing. To Surpass The Last Experiment This Flow Rate Must Be Maintained For At Least Thirty Two Seconds-” Gaster paused, tilting his head at something. A moment later Sans could hear it too: a high pitched wail was quickly rising over the noise of the extractor, growing more shrill each passing moment. Was something broken? It seemed to have caught Gaster off guard.

“It- It Appears The Subject Has Awoken,” Gaster said. The word spun around Sans’s head as he tried to make sense of it. _Subject_? That sound, it wasn’t… it couldn’t be…

The screaming persisted as Gaster continued to take notes. “...Being Melodramatic, Likely. This Level Of Stressor Should Not Be Enough To-” The video skipped, and suddenly Gaster seemed much more concerned. “-Off! Shut It Down!” The howling continued even as the lines of purple light began to unwind from the machine. There was another skip. “-o, No, No!” Though the machine now appeared dormant, the yellow glow in the extraction tubes persisted, the fluid light still draining away. The hum of the machine began to fade and the screams also started to falter. Gaster dashed over to the machine, pushing against a section of skull as the device split open with a hydraulic hiss. Gaster was still speaking - there was another jump in the footage - though he was too far away from the camera for his words to be made out. Sans was unable to look away as Gaster reached into the maw of the skull, pulling something small and dimly glowing from the machine’s depths. The light stuttered as it was removed, growing steadily more faint. Though the camera was on the other side of the room, Sans was able to clearly make out the shape of the figure that Gaster removed from the Extractor. It was small, and frail, and unmoving.

A child.

_A child._

Sans sucked in a breath, unable to believe what he was watching. No, he couldn’t - Gaster would never do such a thing - and yet the video was too clear to doubt -

Sans leaned heavily against the counter as the world seemed the spin and he struggled to not be sick. On the screen Gaster had sent a flurry of hand constructs away, and they now were returning with a glass container. The hands quickly unscrewed the device, scooping the flickering yellow soul into the jar. Gaster clamped the top back onto the container, sealing the lid with a flash of magic. The soul’s light stabilized, even as all the tension went out of the figure it had belonged to.

“oh god,” Sans choked.

“Sans.”

Sans spun towards the door, lances of cold fear stabbing through him. Gaster stood in the doorway, regarding his assistant. “You Shouldn’t Be Down Here,” he said.

“g-gaster,” Sans stammered, his mind still spinning. “h-how? why are you here?”

“I Felt The Extractor Powering On,” Gaster explained. His voice was level and cold. “I Didn’t Expect It To Be You.”

Sans found himself shaking. “gaster, what-” his voice broke, and he had to fight to keep from taking a step back. He gestured wildly towards the time machine and video recorder. “what _is_ this?”

Gaster’s gaze slid over to the video Sans had been watching, and an unreadable expression passed over his face. “Ah. That Is… Going To Take Some Time To Explain.”

“ _explain?_ ” Sans spluttered. “you- you _killed a child!_ ” Sans was still shaking, though now fear was quickly subsiding to confused anger. “what- how could you- a _child_ , gaster!”

“As I Said, I Can Explain,” Gaster said, remaining cool. “The Extraction Process Was Not Intended To Kill It-”

“they were _screaming!_ ” Sans interrupted, angry tears springing to his eyes. “they were in _pain!_ and you were just- just _experimenting_ on them like some kind of lab rat!” The light from Sans’s blasters was growing as his emotions heightened, and his eyes flashed with magic.

Gaster frowned. “You Don’t Understand The Context,” he said. “It Was A Desperate Move, Yes, But There Was No Guarantee We’d Find Another Human To Work With. Human Souls Are Valuable, Sans, And We-”

“do you even hear yourself?” Sans demanded. “you sound like you’re talking about some kind of - some kind of endangered species, but _we’re_ humans, gaster! we’re humans, too.”

“No, Sans,” Gaster said, looking at his assistant sadly. “You Know We Are Not. Not Anymore, At Least.”

Sans shook his head in disbelief. He could feel his magic coursing through him in anger and frustration, threatening to overflow at any moment. “it’s just that easy for you? just - just like flipping a switch? we’re not human any more so it doesn’t matter if you _murder_ a couple?”

“Sans,” Gaster objected. “It’s More Complicated Than That. Just Let Me Explain.”

“i can’t,” Sans said. The video had run its course and turned to static, but he couldn’t stop seeing the image of the child going limp as Gaster took its soul. He was still filled with incredible amounts of anger - and even fear - but at that moment, reliving that thought, he felt a wave of crippling heartbreak.

“i can’t listen to you right now,” Sans said more quietly, magic stinging at his eyes as the tears finally broke away and rolled down his face. He couldn’t look at Gaster, couldn’t bear to be there any longer for fear he’d do something rash. And he _wanted_ to something rash, too. He wanted it badly. But it was too much to take in all at once, and he needed time to process.

“Sans, Wait-” Gaster started, but Sans was already teleporting away.

He landed in his room, whereupon he immediately staggered to his bed. Sans sat down, taking a shuddering breath and trying not to be sick. There were so many thoughts he was trying to process he didn’t even know where to start. A child. Gaster had killed a child. How could he have done such a thing? How could he possibly justify it? Did Sans even know Gaster at all? He knew the scientist had been here for several years, but could someone really change that much in just-

The world warped, and Sans’s stomach lurched, and he was suddenly back in the lab. He blinked, momentarily confused, until Gaster began to talk.

“Please, Sans,” Gaster said. “I’m Just Trying To Explain.”

Sans’s temper flared, realizing the scientist had done a time jump to pull him back. “don’t do that,” Sans glared. “i said i didn’t want to talk!” Once more he teleported away, but this time he was only in his room for a moment before it lurched back to the lab.

“Try To Be Reasonable, Sans,” Gaster continued.

“gaster,” Sans growled. “let me go.”

“Not Until You Hear Me Out,” Gaster said. “I’m Merely Trying To Ensure That You Have All Available Facts Before You Form An Opinion About My Actions. I’m Just Asking That You Act Rationally.”

“ _rationally?_ ” Sans spat. “ _Rationally?_ You really want me to act rational? ‘Cause I’m the mother-fucking _picture_ of restraint right now.” His blasters began to hum dangerously, and Gaster took a step back, blasters of his own forming in instinctive response. Dangerous intent rolled off Sans in waves. “But if you want to see me be rational? You want to see me act on how I _really_ feel?” His left eye flashed blue. “Go ahead. Pull me back again. _Just. Try me._ ”

Gaster didn’t speak, and the sets of blasters stayed trained on each other with tense focus. For several long moments neither Sans nor Gaster moved, allowing their magic to speak for them. Sans wasn't thinking - wasn't wondering if Gaster really had it in him to kill his apprentice. It would be easy, after all - just one hit was all it would take. But Sans didn't care about any of that. More than anything, he just wanted to hurt this person who'd hurt a child. He was waiting for an excuse - any excuse - to let his blasters be conduits to his anger.

But Gaster didn't move. Perhaps he knew that Sans was waiting for him to make a move. Even now Gaster wasn't giving Sans what he wanted: the thought made his blood boil. With a frustrated growl Sans finally teleported away, appearing in his room for the third time.

His blasters still hummed angrily, and he very nearly let them blow a hole through his wall before he banished them with a frustrated gesture. Instead he grabbed his pillow, punched it, threw it against the wall, and then fell back on his bed with a sob.

This time, Gaster didn’t pull him back.

 

 

 

 

**Notes for the Chapter:**

> Sans can speak in Uppercase when he's really upset (and has before) just as Papyrus can speak in lowercase if he's being particularly quiet. 
> 
> So a lot of stuff happened in this chapter; I hope it all made sense. I was intentionally vague in some places and tried to be transparent in others. If anyone's confused about anything, let me know and I'll do my best to explain. 
> 
> Three chapters to go. Thanks for reading!


	16. > Act

**Summary for the Chapter:**

> A chapter in which people try to get Sans to use his words.

**Notes for the Chapter:**

> Ugh. Soooooooo the total chapter count goes up by one! (Again.) I'm sorry guys, this chapter was just getting so long that I had to break it in half. It also might be a little slow because of where I had to break it T-T On the bright side, the next chapter (i.e. the other half of this one) should be done in a day or two. 
> 
> You can't knock down the pieces before you finish setting up all the dominoes - bear with me, guys. 
> 
> Um. Take this doodle I did from last chapter as an apology? 
> 
> http://img06.deviantart.net/ad6b/i/2017/156/b/3/sans_and_the_extractor_by_kiarasa-dbb4sbq.png

 

 

For the next two weeks Sans didn’t speak to Gaster. He continued to go to the lab and continued to work on the projects with which he’d been assisting, but at the slightest indication Gaster would be in the area Sans teleported away. Maybe it wasn’t the most mature way to deal with it, but Sans wasn’t ready to face him yet.

Sans was lost. He was confused and depressed and still so, so angry. He’d known about the human souls - he’d known the King was waiting on one more before they’d be able to leave the Underground. Yet he’d never really questioned how the souls had been taken. At one point Gaster had said that the humans had been seriously injured in their fall to the Underground - and like a fool, Sans had believed him. How naive he had been. How blindly trustful.

Sans wondered how many of the others Gaster had killed.

 

He hadn’t planned on ending up in the King’s soul room, but Sans was there regardless. In the past he and Gaster had visited the chamber to tend to the souls - routine checkups to ensure that none of their magical potential was dissipating from no longer residing in a body - though there was no particular reason for Sans to be there now. Sometimes, when Sans was wandering or not paying much attention, his shortcuts took him to places that happened to be on his mind; he suspected much the same had happened now.

Sans almost left. The souls, in each of their jars, were neatly spaced across a countertop. There was a gap where one of the souls was missing - the green one - but it was the yellow that caught Sans’s eye. He stared at it for several minutes, his mind in another place. It wasn’t until a voice cleared itself at the edge of the room that he turned, finding Alphys standing in the doorway.

“oh. hey,” he said, glancing towards the scientist. Alphys fidgeted, the jar with the green soul clutched in her claws.

“U-um, hi Sans,” Alphys said. Her eyes flickered to the souls. “W-what are you doing here?”

Sans shrugged. “nothing, i guess. just about to leave.” His gaze shifted down to the soul she was carrying. “you?”

Alphys shuffled over to the counter, nervously placing the jar back with the others. “Oh, um. I w-was just taking this back… J-just a routine checkup, Gaster asked me to d-do it since you’ve been… um… I mean…” Alphys wrung her hands as she stepped away from the counter, staring at her feet. “S-sorry, I-I probably shouldn’t ask, but… I-it seems like you and Gaster have been avoiding each other recently. W-what happened between you two?”

Sans nearly deflected the question, but Alphys couldn’t be blamed for being curious. Especially if it was affecting her work. She probably deserved to know - some of it, at least.

“we... had a fight,” Sans admitted. “guess you could say we don’t see eye-to-eye on some things, heh.” He smiled as the joke, but even just recalling the encounter with Gaster was stirring his frustration once more.

“I s-sort of figured,” Alphys admitted. “You’ve both been p-pretty distracted lately.”

Sans laughed, though it came out more as a huff. “i don’t know what _he’s_ so worked up about.”

“W-well,” Alphys said, her stutter and anxiety growing even more apparent, “Y-you guys seemed pretty close b-before, s-so I, um, I guess h-he probably just m-misses working with you-”

Sans snorted. “yeah. i’m sure that’s it.”

“Well what else w-would it be?” Alphys said, squinting at Sans’s tone in concern. “W-whatever you guys fought about… I-it couldn’t have b-been _that_ bad, right?”

Sans was silent for a moment, his gaze returning to the souls. “did gaster ever tell you where he’s from?” Sans mused. “he and paps and i? before we came here?”

Alphys frowned. “I-I don’t...” she hesitated. “What are y-you trying to say, Sans?”

Sans shook his head. “nevermind. doesn’t matter, anyway.”

Alphys waited for him to continue, but Sans remained quietly staring at the souls.

“W-what’s wrong, Sans?” Alphys finally prompted. “W-what’s been bothering you?”

Sans let out a sigh. He hadn’t wanted to bring it up with Alphys, but questions had been itching at him every since he’d visited the old lab. Gaster would likely have been able to answer anything he wanted to know, but… Alphys seemed like a better alternative.

“alright,” Sans said. “i’ll ask, because i hafta know, but i don’t expect you to answer. it’s okay if you don’t.” Sans gave Alphys a sidelong look. “how’d we get these souls, alphys? how’d the humans die?”

“Oh,” Alphys squeaked. “Oh. _Oh_. Is th-that what…? Oh dear…” Alphys went back to wringing her hands, this time a small tremble accompanying the motion. “Oh dear… I- w-well…” She swallowed, then nodded to herself and tried to take a composing breath. “U-Undyne captured them a-after they fell. Th-the first o-one she killed... I a-almost d-din’t get its soul into an i-incubator in t-time.” She swallowed again, looking everywhere in the room but at Sans. “A-after that she w-was more careful. Sh-she’d bring them to Asgore s-so w-we could collect to souls a-after… after… he killed them.” Alphys shot Sans a quick glance; he was watching her with an impassive expression.

“all of them, alphys?” Sans asked quietly, turning back to the souls. “...even the yellow one?”

Alphys gave a small, startled hiccup. She floundered over her words for a few seconds before she found her voice.

“Are…” she started. “Are y-you asking that b-because you already know?”

Sans chuckled softly. “yeah, i guess i am. how cliche is that?”

Alphys sniffed. “I’m s-sorry, Sans. I’m sorry. W-we - Gaster and I - we’ve both d-done things we’re not p-proud of. I-I wish we c-could fix what w-we’ve done, b-but we can’t t-turn back time-”

Sans laughed, causing Alphys to jump. “sorry,” Sans chuckled, shaking his head. “sorry. it’s just funny - no, i guess it’s not that funny. ironic’s more accurate. irony get’s you every time, ya know?”

“S-Sans,” Alphys said. “I-I’m worried about you. I- I think Gaster’s worried a-about you, too.”

Sans’s laughter tapered off as he turned towards the door. “nah. it’s fine. i’m okay. i just had to know the whole story. so. thanks for telling me, alphys.” He began to leave.

“W-Wait, Sans,” Alphys said, stopping him. “I-it’s not me you sh-should be talking to a-about this. Please. Just t-talk to him. J-just give him a chance.”

For a moment it seemed like Sans was about to reply. He stopped, his head half turned back towards Alphys. Then he shrugged it off and left.

 

It was the middle of the day, but Sans decided to cut out early. His mind was in a haze and he was no good to anyone, let alone his work, when he got like this. Then again he hadn’t been much better any day these last few weeks, but there was little he could do about that.

Sans nearly teleported home for a nap when he recalled Papyrus was likely to be there, getting everything cleaned up. They’d finally decided to buy the house in Snowdin, and tonight they were having a housewarming party. Sans sighed in remembering the party. Hanging out in a crowded house was the last thing he wanted to deal with right then. He’d suck it up for his brother, but in the meantime…

Sans took a shortcut to Waterfall.

Whenever Sans was stuck on a problem he liked to visit the area. Maybe it was the bioluminescent glow of the flowers, or the gentle hush of the streams, but the marshes always helped to put his mind at ease.

It could also be fun.

“gaster,” Sans said, finding a nice bank to sit down at, “is an ass.”

“...ass,” the flowers chorused, each picking up a snippet of each other’s echo. “...Gaster… ass… is an… Gaster is an... ass…”

Sans chuckled. “heh, you tell ‘em.”

The flowers continued their muttering.

“and he’s a bad scientist,” Sans added.

“...bad… and he’s a.... scientist… bad scientist…”

Sans dangled his feet over the bank, kicking them back and forth in the air above the creek. “and a bad friend,” Sans said, watching the water.

“...friend… bad friend…”

Sans didn’t say anything more, letting the words of the echo flowers die out on their own.

He didn’t know what he was doing here. This wasn’t an equation he could solve by sitting and thinking about it - he’d been doing that for two weeks and hadn't gotten anywhere. And he knew he couldn’t keep it up indefinitely.

“what do you think?” he asked the nearest flower. “should i talk to him?”

“...talk...what do you… to him… should i… talk… you think… talk to him…”

“hm,” Sans nodded thoughtfully. “you make a compelling argument.”

A flower giggled.

Then another, and another - a surge of echoed laughter suddenly swept through the field, rising like a wave. Sans stood up as the laughter rushed around him, and he turned about trying to find where the sound had originated. The voice sent a shiver down his spine; he’d heard it before, in the old lab.

“who’s there?” he called, barely audible over the chorus of giggles. The laughter swirled around him, mocking him.

“what do you _want_?” he demanded. Still there came no response. His questions mingled with the laughter, turning the giggling flowers into a cacophony of confused noise.

“why are you following me?” Sans asked again. “who _are_ you?”

The laughter began to fade, one by one the flowers falling silent and the echoes fading out. Nothing bothered answering his questions.

“heh,” Sans sighed, looking over the silent field. “this is startin’ to get kind of old.”

He was about to sit back down - or teleport somewhere else, he hadn’t quite decided yet - when he caught a flicker of movement. Still on edge from the laughter, Sans’s magic threatened to form blasters. Sans held the weapons back for now, but kept them at the ready. He squinted at the glimmer of light in the darkness, trying to make out the form. It was tall, it’s face white - Gaster? (And for a moment Sans recalled the Gaster-like thing he’d encountered in the old lab, though even now the memory seemed more like a dream.) But no, it wasn’t Gaster; as the monster approached, its gait became undeniably familiar.

“...bro?”

“SANS!” Papyrus cried, practically skipping through the marsh. “I THOUGHT I WOULD FIND YOU HERE!”

Sans blinked in confusion. “what are you doing here?”

Papyrus slowed only the moment before he was about to barrel into his brother, and he used the momentum to sweep Sans up into a hug. Sans couldn’t help but laugh at the unexpected embrace; his brother’s enthusiasm was contagious.

“AS I SAID, I WAS LOOKING FOR YOU!” Papyrus said, setting his brother down. “ALPHYS TOLD ME YOU LEFT EARLY.”

“aw, geez,” Sans said, sinking down into his coat. “she called you? that wasn’t necessary.”

“HM, MAYBE,” Papyrus considered. “BUT SHE SAID YOU SEEMED OFF, AND I MUST AGREE THAT YOU HAVE BEEN A BIT MORE QUIET THAN USUAL RECENTLY.”

Shit, even Papyrus had noticed? Sans would have to work on that. But he should have known better than to talk to Alphys - she couldn’t keep anything to herself.

 _Probably already told Gaster all about our conversation, too,_ Sans thought glumly.

“i’m fine, bro,” Sans said. “just, you know, keeping busy at work is all.”

“SO YOU LEFT WORK EARLY?” Papyrus raised an incredulous eyebrow. “ALPHYS SAID IT HAD SOMETHING TO DO WITH DOCTOR GASTER.”

Sans decided he was going to have a talk with Alphys after this. There would be words.

“look, it’s nothing, paps,” Sans sighed. “we just had a fight is all.”

“AH,” Papyrus said, taking a seat where he’d been standing and settling in. Even sitting down he was nearly as tall as Sans. “WAS IT A BAD FIGHT?”

An image of Gaster’s powered-up blasters, aiming straight at Sans, flickered through his mind. “yeah, i guess you could say that.”

“WHAT WAS IT ABOUT?”

Sans didn’t mind talking to his brother about things but this… this was too much. How could he possibly tell his brother that Gaster - someone Sans had considered a friend - had killed a child? It would break his heart.

“it was about something gaster did,” Sans said, sitting down next to Papyrus. “Something really… unethical.”

“I SEE,” Papyrus said. “AND YOU TRIED TO STOP HIM?”

“nah,” Sans admitted, grateful Papyrus wasn’t pressing for details about what the act actually was. “nothing like that. i found out about something gaster did a long time ago.”

“OH.” Papyrus was listening to his brother with a very focused attention. “AND HE KEPT THIS FROM YOU?”

“yeah,” Sans said running his hand over his skull in frustration. “probably never would have told me if i hadn’t found out.”

“DO YOU THINK IT’S BECAUSE HE REGRETS IT?” Papyrus asked.

Sans frowned. “what? why do you think that?”

“MAYBE HE DIDN’T TELL YOU BECAUSE HE REGRETS IT,” Papyrus said. “MAYBE HE’S SORRY.”

“sorry? i- i don’t know, paps,” Sans said, a little flustered. He actually hadn’t bothered to think about that before now. “maybe, i don’t know. does that even matter?”

“OF COURSE!” Papyrus exclaimed. “BEING SORRY ALWAYS MATTERS. EVERYONE MAKES MISTAKES, SANS.”

“this was a pretty big mistake, bro.” Sans shook his head. “ _assuming_ it even was an accident.”

But perhaps Sans wasn’t giving Gaster enough credit. He still recalled the videos he’d watched - Gaster had seemed pretty broken up over something in the first one. Sans felt his stomach twist unpleasantly; he didn’t like where Papyrus was going with this.

“HAVE YOU ASKED HIM?” Papyrus asked. “IF HE REGRETS IT?”

“...no,” Sans admitted. “we haven’t talked much.”

“WELL, THEN,” Papyrus said, folding his arms as if the matter were settled. “THAT’S WHAT YOU SHOULD DO.”

Sans grimaced. “i dunno, paps. it’s just… it’s just that he _hurt_ someone,” Sans said, coming as close to telling his brother the truth as he likely ever would. “and even if he does regret it - you can’t undo that, you know? it doesn’t change what he did.”

“I THINK,” Papyrus said, speaking slowly as he considered his words, “THAT WHO A PERSON IS NOW - OR WHO A PERSON IS TRYING TO BE - IS MORE IMPORTANT THAN WHO A PERSON WAS. AND I ALSO THINK THAT ANYONE CAN CHANGE. THAT ANYONE CAN BE A GOOD PERSON IF THEY TRY.” Papyrus tilted his head at his brother. “YOU JUST HAVE TO GIVE HIM A CHANCE.”

Sans groaned, running his hands down his face. “man. i’d really rather not.”

Papyrus grinned, seeing he’d already won his brother over. “NYEH HEH HEH! WHAT SORT OF BROTHER WOULD I BE IF I COULDN’T TALK YOU INTO DOING THINGS YOU DON’T WANT TO DO!”

“no brother of mine,” Sans chuckled. He blew air out his nose. “thanks, paps. i guess i probably needed to hear that.”

“OF COURSE YOU DID! THAT IS WHAT I AM HERE FOR.” Papyrus pulled Sans into a one-armed hug, burying Sans’s head in his side.

“heh heh. you’re squishing me, bro.”

“IT IS A LOVE SQUISH!” Papyrus declared, releasing Sans regardless. “SO YOU’LL GO TALK TO HIM?”

“yeah, guess so,” Sans reluctantly agreed.

“EXCELLENT!” Papyrus exclaimed. “INVITE HIM TO THE PARTY TONIGHT AS WELL! THE MORE THE MERRIER!”

“the party?” Sans looked incredulous. “that’s pushing it, bro.”

“WELL, I CAN TRY,” Papyrus grinned.

“i don’t even know why you want to invite him,” Sans said, a smile twitching at his cheeks. “there’s already going to be a skele- _ton_ of people there.”

“GOOD GRIEF, SANS,” Papyrus snorted. “YOU _MUST_ BE FEELING BETTER.”

“yeah,” Sans said. “a skele- _to_ -”

“ALRIGHT, ALRIGHT!” Papyrus shooed away Sans’s pun. “GET GOING ALREADY! YOU’LL BE HOME IN TIME TO HELP SET OUT THE SNACKS, YES?”

“sure, bro,” Sans chuckled. “be home soon.”

**Notes for the Chapter:**

> Thanks for reading!


	17. Gaster

**Summary for the Chapter:**

> A chapter in which Gaster has a lot to say. 
> 
> (A little heavy on exposition. I'm sorry ._.)

His smile died outside of Gaster’s door. It was one thing to promise Papyrus things, and quite another to follow through. Sans hated making promises.

Sans knocked on the door, then opened it up without waiting for a response.

“Yes?” Gaster said, bent over his desk. He looked worse than Sans remembered; shadows hung about his eyes, and he was worrying the crack in his forehead.

“uh. hey, doc,” Sans said, hovering in the doorway. Gaster looked up in surprise. “...can i come in?”

“Oh- Of Course, Sans,” Gaster said, his constructs springing into a flurry of movement as they began straightening papers about his desk. “Come In - Sit Down. Is There… Do You Need Something?”

Sans stepped inside, but felt too tense to sit down. “...i’d… like to talk with you,” Sans admitted, forcing the words out. “if you have time. i’m ready to listen.”

“Listen?” Gaster didn’t seem to be at all prepared for Sans’s visit. “Oh- You Mean- Yes… Yes, Of Course I Have Time. I, Ahm… Where Would You Like Me To Start?”

Sans closed the door softly behind him, then leaned back against the wall. “i dunno,” he admitted, giving Gaster a weak smile. “i hadn’t thought that far ahead. i guess… the kid. it’s as good a place to start as any.” Gaster nodded, straightening the front of his coat as he collected himself. Once more he appeared all business and reason - the jittery movements of his constructs, however, betrayed his nerves.

“were there more, doc?” Sans started. “were there other kids that you…?”

“Others?” Gaster echoed, comprehension slowly dawning on his face. “Stars, No. _No_ , Sans, It Was Only… Only The One Human. There Were Others To Fall Before The Yellow Soul, But Most Were Before My Time.”

“yellow soul,” Sans repeated. As if they weren’t even a person. Sans was trying to keep an open mind, but Gaster wasn’t making it easy. “did you even know their name?”

“No,” Gaster admitted, looking away from Sans. “I… I Never Asked. I Thought It Would Make It Easier.”

“what, torturing them?” Sans asked, an edge biting into his voice.

Gaster grimaced. “It Wasn’t Intended To Be, Though I Won’t Attempt To Deny It. What I Did Was… Wrong. And Trust Me, Sans, I Do Regret It. At The Time, However, I Believed It Was The Best Course Of Action I Could Take.” Gaster once more met Sans’s gaze, this time refusing to look away. “I Know That You Judge Me, Sans. I Understand. I Do As Well. If You Really Want To Hear Me Out, However, Then The Full Story May Take Some Time.”

Sans folded his arms. “i got all day.”

Gaster nodded shortly, steepling his fingers together as he sorted through his thoughts.

“When I First Came To The Underground,” Gaster began, “Getting Back Was All I Concerned Myself With. Those First Few Days Were A Very… _Confusing_ Period of Time, But Once I Had Grown Accustomed To My Situation, I Set My Sights On Returning Home. I Soon Became Aware Of Scientists Working For The King, And Saw This As The Opportunity I Was Looking For. With The Royal Labs At My Disposal, I Would Have Nearly Unlimited Access To All The Resources The Underground Had To Offer. I Applied For A Position On The Team, And Was Quickly Accepted.

“Climbing The Ranks Was Embarrassingly Easy. Only Alphys Seemed To Wield Any Natural Talent For the Sciences - And Scientific Texts, Here, Are Very Sparse. Most Of The Technology In The Underground Had Been Backwards Engineered From Pictures And Videos That Had Survived The Waterfall - Needless To Say, My Experiences Proved Invaluable. I Worked On Plans For The Timemachine, In Those First Few Years, But I Also Revolutionized The Core. I Repair Computers - I Created An Intranet. I Invented Fusions Of Machine And Magic. I Provided Electricity To Areas Of The Underground That For Countless Years Had Gone Without. I… I Was _Helping_ People, Sans. And Somewhere Along The Way, I Stopped Working On The Timemachine. I Stopped Trying To Go Back.

Gaster tapped his fingers together, staring off into space as he thought. “I Had Been Here For Three Years When The Human Fell. They Made It Further Than The Others, I’m Told, But They Were Captured Regardless. Undyne Took Them To The King, For Asgore To Finish. I Stopped Him, However. I Asked If I Could Try Something First, And He Agreed.

“Before I Came Here, Alphys Had Performed Many Experiments With Soul Extract. I Won’t Get Into The Details Of Why - But Suffice To Say That We Had Some Small Data To Go On, And I Had An Experiment I Wanted To Try. I Thought That Since Magic Could Be Extracted Directly From The Soul Of A Deceased Human, That Perhaps It Could Be Extracted From A Living One As Well.”

“ _why_ , gaster?” Sans couldn’t help but interrupt. “if you’d convinced the king to hand the kid over to you, why didn’t you let them go? why didn’t you _help_ them?”

Gaster looked surprised. “But I Was Helping Them, Sans. What Else Would You Have Me Do? Find A Monster Soul For Them To Take So They Could Escape Through The Barrier? Release Them Back Into The Underground So They Could Get Captured Once More?” He paused expectantly, but Sans didn’t have an answer. “There Was Nowhere For Them To Escape To, Sans. And Even If They Could, I’m Not Sure It Would Have Been Right To Let Them Leave. We Monsters Are Trapped Down Here, After All. Seven Human Souls Is The Only Way To Buy Our Freedom.”

Sans was shaking his head. “it’s not right. not at that cost. living down here isn’t hurting anyone - why’s our freedom worth more than seven lives?”

“Why Are Seven Lives Worth More Than All The Lives In The Underground?” Gaster countered. “Surely, You Don’t Think We Can Survive Down Here Indefinitely? All Resources Are Finite, Sans. Eventually, One Way Or Another, We Will Run Out Of Food, Or Space, Or The Core Will Grow Dormant And We Lose Our Source Of Warmth And Power - Or The Volcano Will Finally Erupt And End All Of Us.” Gaster shook his head. “We Have To Get Out. It’s Not A Question Of If We Will Get A Seventh Soul, But When.”

Sans’s stomach knotted unpleasantly. He hadn’t ever considered the limited resources of the Underground. “but,” he still objected. “you don’t know any of that for sure. there... there could be another way...”

“Possibly,” Gaster admitted. “But If A Seventh Human Shows Up, Is That Really Something You’d Want To Gamble With? The Possibility Of Some Other Way... Versus A Guaranteed Ticket To Our Freedom? It Would Be One Soul To Ensure The Rest Of Us Have A Future. Would You Not Make That Trade? Even If It Were All Our Lives At Stake? Even Your Brother’s Life?”

The last words hit Sans like a physical blow. He pushed off the wall, shaken. “i-” he said, his mind reeling. Would it really come to that? They weren’t really doomed if they were stuck down here, were they? But his brother… his brother deserved better than a life in a cave. Of course he wanted to get out - to go back home - but he didn’t think he could take a life in his brother’s name. Papyrus certainly wouldn’t want that.

“i... i don’t know,” Sans said. “I’d do anything for paps, but…” But _wouldn’t_ he do anything? _Of course,_ part of him thought. _Choosing between his brother and a stranger wasn’t even a contest._ “s-so, what,” Sans said, in an attempt to distract himself from his thoughts. “you’re just going to kill the next human that falls down here? without any hesitation?”

“Stars, Sans,” Gaster said, looking a little taken aback. “Of Course Not. That’s Not At All What I Meant. Certainly, I Believe It Is Important To Open The Barrier - But I Would Try To Avoid Killing Them, If At All Possible. That’s What I Was Attempting To Do With The Yellow Soul, After All. I Was Trying To Save Them.”

Sans’s brows knotted. “i don’t understand, doc,” he admitted.

Gaster sighed, rubbing the bridge of his nose. “The Extractor. I Thought I Might Be Able To Use It On A Live Human. That, Perhaps, If Some Of Their Essence Could Be Distilled, It Would Be Enough To Break The Barrier In Place Of A Complete Human Soul.” He shook his head, and his voice was softer when he next spoke. “I Failed, As You Saw - Not Only That, But I Put Them Through Great Pain In The Process. I Hurt Them - Then Killed Them - Then Nearly Shattered Their Soul. Such Senseless Suffering. There Had Been Other Tests Before That Last One, But I Never Really Understood The Strain I Was Putting Them Under Until… Well, Until It Was Too Late.” Gaster looked at Sans sadly. “You Watched The Video. Did You Notice The Skips In The Tape?”

Sans had forgotten it until Gaster mentioned it. “yeah... was that...?”

“Time Jumps,” Gaster nodded. “I Tried To Undo It. But The Limitations Of My Magic… No, It Was My Uncertainty That Sealed Their Fate. You See, My Time Travel Is Very Limited. I Can Never Go Back Further Than Any Previous Point In Time That I Have Travelled Back To - That Is To Say, I Can’t Jump Over A Previous Jump. So When My First Time Skip Didn’t Go Back In Time Far Enough To Stop The Extractor, The Child’s Fate Was Sealed. That Didn’t Stop Me From Trying, Of Course, But Each Successive Jump Just Left Me With Less And Less Time Before Their Death. To This Day I Wonder… I Hope They Were Not Aware Of The Time Jumps. That My Attempt To Save Them Didn’t Extend Their Suffering.”

“...fuck,” Sans said, slumping back against the wall as he tried and failed to imagine. How Gaster felt. How the kid must have felt. “fuck, g, i… i’m sorry…”

Gaster tipped his head up to the ceiling. He didn’t seem to have heard Sans. “That’s When I Began Working On The Timemachine Again. I Thought Maybe I Could Save Them. I Thought Maybe I Could Save All Of Monster-Kind. Maybe I Could Save You, And Papyrus.” Gaster chuckled softly. “I Even Thought I Could Save My Marriage. Did You Know?” he asked suddenly, looking at Sans. “That’s Why I Started The Project Back On Our World In The First Place. To Save My Marriage. She Left And Took Our Daughter, And I… Did You Know That’s Why I Started It?” Sans mutely shook his head. Gaster smiled fondly. “I Was Not A Very Good Father - And An Even Worse Husband. Ah, Well. I Think It Was Probably For The Best… And At Any Rate None Of That Matters Anymore. The Point Was, I Thought A Lot Of Things At The Time. My Regrets Fueled My Perseverance As I Built The Timemachine... But When I Finished It, I Couldn’t Bring Myself It Use It. Not Even To Save All The Things I’ve Cared About.”

“why?” Sans asked, finally finding his voice.

Gaster looked at Sans matter-of-factly. “Because I Am A Coward, Sans. Not A Drop Of Nobel Marrow In My Bones. I Trusted That My Math Was Right, But I Was Never Able To Bring Myself To Turn The Thing On. No Matter How Small The Chance Was Of Me Ending Up Somewhere Or Somewhen Else - I Wouldn't Risk It.”

“that doesn’t make any sense, g,” Sans said. “even if it took some calibration… couldn’t you just try again?”

“Perhaps,” Gaster said. “But What Would Happen, Do You Suppose, If We Returned To Our World?” Gaster watched Sans’s confused expression. “A World Without Magic Or Souls. A Reality With Different Physical Laws.”

“you…” Sans looked down at one of his hands. What would happen to a being held together by magic when that power was taken away? “...you… you’re saying… we can’t go home?” No… No, that couldn’t be right.

“I’m Saying,” Gaster said, “I Couldn’t Promise That We’d Survive The Trip. Stars, We Barely Made It Here, Didn’t We?”

“oh.” Sans wandered over to the chair in front of Gaster’s desk, and finally sunk into it. “oh. then we’re really like this for good, huh?”

“In All Likelihood,” Gaster conceded.

Sans tried to digest that thought. He and his brother were probably going to be skeletons for the rest of their lives. They were probably never going to be able to go home. These were their bodies and their world now.

And for some reason, he was okay with that.

He’d been pretty freaked out when he’d first arrived, that was true. But over time the weirdness of everything had just become normal - and anyway, what _was_ there left for them back home? Papyrus was happier here than he’d ever been before, and Sans was challenged and engaged. It was strange, but the idea of not being able to go back filled him with a kind of peace.

“you know, gaster?” Sans said. “i think i can live with that.”

Gaster smiled wearily. “It’s Not Such A Bad World To Live In, Really.”

“even being trapped down here?” Sans asked, some of his previous apprehension returning. “what... what’ll you do when the next human falls down?”

“Whatever I Can To Free Us,” Gaster said. “I’ve Been Working On Plans For A New Extractor, Actually. One That Is More… Refined. I Haven’t Given Up On My Idea To Extract Soul Essence - I Just Hope That This Time I Can Manage It Without Ending Another Life.”

This didn’t inspire much confidence in Sans, but he supposed it was as much as he could hope from Gaster. At least Gaster hadn’t intentionally killed the child - at least he regretted the pain he had caused. Gaster seemed determined to help free the monsters, and Sans didn’t think he’d be able to stop him from trying. The best he could do was be there when the next human fell - watch, and intervene if necessary.

It wasn’t the best of plans, but it was one Sans thought he could manage.

“say, doc,” Sans said, his mind returning to their previous confrontation. “i’ve been meaning to ask. the extractor… that day when i found it - were you down there before?” He was still unable to get the uncanny image of the Not-Gaster out of his mind.

Gaster tipped his head, curious. “What Do You Mean? I Was Monitoring The Core’s Magical Barriers That Day. I Didn’t Leave The Terminals Until I Felt Someone Accessing The Extractor - Though By The Time I Arrived I Didn’t Even Make It That Far When I Saw Your Blasters Glowing Inside My Old Office. Why Do You Ask?”

Sans hummed to himself. “i’m not sure. i guess i thought i saw you down there - or just something that looked like you. it was creepy as hell, and that laughter wasn’t helping.”

“Laughter?” Gaster asked.

“yeah,” Sans grimaced in remembrance. “i guess more like giggling. it was pretty weird. i heard it a couple times while i was down there… actually i heard it again just today when i was in waterfall. never did figure out who that was. just kind of thought my nerves were getting to me.” Sans shrugged.

A spark of irritation - accompanied by the purple glow of his magic - flashed through Gaster’s eyes. “Oh, I Have A Decent Idea What That Laughter Belonged To. Damn, I Told It To Leave You Alone, Too.” Gaster let out a growl of frustration, surprising Sans. “I Should Have Known Better Than To Trust It Would Heed My Threat.”

Threat? Sans didn’t like the sound of that. “what the hell are you talking about, doc?”

Gaster scowled, massaging one of his cracks. “And Old… Adversary. It’s Plagued My Existence Since I Came To The Underground. I Was Worried It Would Take An Interest In You And Your Brother As Well, And I Warned It Not To - Though I Must Admit I Am Unsurprised To See I’ve Been Ignored.”

“it?” Sans pressed.

“Flowey,” Gaster spat.

Sans couldn’t hold back his snort. “flowey? what kind of a name is that?”

“An Accurate One,” Gaster said, completely unamused. “That’s What It Calls Itself, Anyway. It May Act Innocent, But It Can Be Very Dangerous. Lord Knows It’s Tried To Take My Life On Multiple Occasions. You Would Be Wise To Keep Your Distance, Sans.”

“so it’s a flower monster?” Sans asked, trying to imagine how a flower could be dangerous.

“Yes And No,” Gaster said. “It Takes A Flower Form, But Calling It A Monster May Be Too Kind. It Doesn’t Have A Soul, For One.”

Sans raised an eyebrow. “i thought that wasn’t possible.”

“Flowey Appears To Be A Special Case,” Gaster said. “I Know Something Of Its Origin, Though Certainly Not The Whole Picture. And From What It’s Told Me - Back When It Pretended To Be My Friend And Before It Got Bored Of Me, - It Carries An Incredible Power.” Gaster paused, casting a suspicious glance around his office. “Forgive My Paranoia,” he said a moment later, “But When You’ve Dealt With It For As Long As I Have…”

“heh, no worries,” Sans said, looking around as he suddenly felt a little paranoid himself. “but don’t _leaf_ me hangin’, doc. what kind of powers are you talking about?”

“Temporal Powers,” Gaster said. “Akin To My Own. It Called Them ‘Save Points,’ Which Let It Go Back To Specific Points In Time - Much Bigger Jumps Than Anything I’m Capable Of. Or At Least,” Gaster added, “That’s What Flowey Claimed. Apparently, Its Ability To Time Travel Ceased When I Came To The Underground. As If Somehow My Abilities Overrode Flowey’s.” Gaster stroked his chin in thought. “It’s A Curious Conundrum, One I’ve Yet To Figure Out. I Probably Would Have Thought The Creature Was Making It Up If It Hadn’t Started Trying To Kill Me. To - As It Said - ‘Seize Control Of The Timeline’ Once More.” Gaster gave Sans a hard look. “This Is Why I Am Concerned It Has Taken Some Interest In You. Be Careful. If It Realizes You Are Cognizant of Time Jumps, It Might Begin To Target You and Papyrus As Well.”

Sans frowned in concern, wondering if his brother had had any encounters with the flower. “but doc,” Sans realized, “you said it doesn’t have any powers anymore. how’s it dangerous? what’s it done?”

“Nothing Much On Its Own,” Gaster admitted, “But Don’t Underestimate The Power Of Carefully Crafted Words. It Has A Particularly Irritating Knack For Getting Under Your Skin. It…” Gaster hesitated. “It Mocked Me After I Killed The Human. Mocked Me For Trying To Save Them. The Things It Said - It Made Me _So Angry,_ Sans. So Much So That I Killed It.” Gaster waved off Sans’s shocked look. “Don’t Give Me That - I Brought It Back With A Time Jump A Moment Later. And Then, To My Astonishment, Flowey Mocked _Me_ For Not Having The Mettle To Commit To The Kill. I Think That’s The Moment It Stopped Taking Me Seriously.” Gaster shook his head. “I Believe That Flower Is Psychotic.”

“ah, shit,” Sans groaned, knocking his head back against the back of his chair. “psychotic - i think you’re right about that. you know i just was thinking… that day when i was exploring the lab, it was the laughter that led me to your old office and the video camera. man, what a chump.” he laughed weakly. “i was played so hard.”

Gaster scowled. “Wonderful. Another Event To Add To The Ever-Growing List Of Ways Flowey Has Attacked Me. I’m Almost Impressed. It Is Always Finding New And Creative Ways To Hurt Me.”

There was a moment of silence.

“hurt?” Sans ventured, watching Gaster. The Doctor was examining something particularly interesting on the cuff of his coat.

“Well, Yes,” Gaster admitted, fiddling with the button. “Your Discovery Of Those Tapes - It’s Caused Irreparable Damage To Our Friendship. And I Don’t Blame You For That, Of Course. However… I Would Have Rather Liked You To Find Out Some Other Way. I Would Have Told You Eventually… In My Own Time. A Better Way.”

“...you think our friendship’s irreparable?” Sans asked.

The response was slow to come. “I Don’t Know,” Gaster admitted. “I’d Rather It Not Be… But I Don’t Believe That’s Up To Me.” His gaze reluctantly returned to Sans.

Sans wasn’t sure he knew either. Gaster had seriously betrayed his trust. And even this session with him now had turned up almost as many new concerns as assurances. Gaster… wasn’t the same man he used to be. Or maybe Sans had just never really known him that well to begin with. They had very little in common, after all, but that hadn’t been a problem before. Gaster took Sans seriously, and laughed at all his stupid jokes, and always trusted him to solve problems others couldn’t. Sans had liked working with Gaster… and he didn’t like the idea of never working with him again.

“i don’t think it’s irreparable, doc,” Sans finally said. Gaster visibly sagged at Sans’s words as the tension drained out of him. “i think maybe it’ll just take some time for us to figure all our shit out… but i think we can figure it out.”

“Time Is One Thing I Have Plenty Of.” Gaster smiled slightly at his own joke. “But… I Am Relieved To Hear That. I Want To Fix Things, Sans. I Want To Be Better.”

“heh, one thing at a time, g,” Sans grinned. “If you want to be a better person, you better talk to papyrus - and you’ll have to get in line ‘cause i ain’t perfect, either. how about… no more secrets,” he offered. “that’s a good place to start.”

“After This Afternoon’s Talk, I Don’t Think There’s Much More For You To Learn About Me,” Gaster said. “But Those Are Definitely Terms I Can Agree To. No More Secrets.”

Sans nodded. “good. and while we’re at it, i want you to let me help out at the terminals when the core’s acting up.”

Gaster raised an eyebrow. “What Is This, Negotiating Your Raise?”

“well, if you’re offering…”

Gaster snorted. “You Know It’s Too Dangerous.”

Sans rolled his eyes. “well that’s why you gave me blasters, wasn’t it? i can watch out for myself. and if things get too heavy, i can always teleport out. come on, g,” Sans pressed. “if you really want to make things right, you gotta trust me.”

“I Do Trust You, Sans,” Gaster said. “I Trust You Completely. However I’m Also Allowed To Be Concerned For Your Wellbeing.”

Sans merely stared at Gaster, waiting for him to relent. It didn’t take long.

“Alright,” Gaster sighed. “If You’re Careful. You Can Assist Me On Monitoring The Core As Well.”

“excellent,” Sans said, rubbing his hands together. “then there’s just one last thing.”

Gaster groaned. “This Is Extortion, Sans.” The smaller skeleton chuckled.

“we’re having a housewarming party at our house tonight,” Sans said. “paps wanted me to ask if you would come.”

“A Party?” Gaster appeared caught off guard by this latest request. He blinked, then slowly smiled. “Well As Long As _Papyrus_ Wants Me To Come,” Gaster said, “I Think I Can Find The Time.”

 

\---

 

Gaster hadn’t been to any parties before. He was not, as they say, a social animal. He’d been invited to a handful of events in the past, but out of disinterest or, more often, forgetfulness, he’d never attended any of them and eventually people had stopped asking. This occasion, however, was different. This time it sounded like it could be… fun.

And more than a little daunting. Gaster did not know how to party. Sans had indicated it would be a very relaxed ordeal, but Gaster was of the opinion that Sans considered _everything_ to be a relaxed ordeal. Was his black lab coat too formal for such an occasion? Would the other invitees find socializing with their boss to be awkward?

Gaster soon learned the answer to both these questions.

“heh, nice coat, doc,” Sans said, letting Gaster in. Sans was wearing one of his signature hoodies, which seemed to be his go-to when he wasn’t wearing a labcoat at work. Others appeared to be in casual attire as well; even Alphys was wearing a dress.

“Perhaps I Should Change,” Gaster mused. Not that he had many options in the way of casual wear.

“too late, you’re already here,” Sans said, shutting the door behind him. “and papyrus has assured me no one’s allowed to leave until the party’s over.”

“When’s The Party Over?” Gaster wanted to know, though Sans didn’t get the chance to respond.

“OH! IT IS DOCTOR GASTER!” Papyrus said, emerging from the kitchen with a platter of smoking… something. “I DID NOT KNOW IF SANS WOULD ASK YOU TO COME! HE HAS BEEN VERY MOODY LATELY.”

“thanks, bro.”

“Ahm, Thank You For Having Me,” was all Gaster could think to say.

“make yourself at home,” Sans said, waving vaguely towards the living room. “i gotta help paps with the table. be there in a bit.”

The home in question was rather small for a party, and almost uncomfortably full, though there couldn’t have been more than ten guests in attendance. Gaster recognized Undyne, Alphys, and a handful of other scientists - the rest, he assumed, might be neighbors from Snowdin. There was one couch (taken by two of his coworkers) and no chairs. A little sparse, but then again the brothers had only just moved in.

Gaster stood about, unsure how to insert himself into a conversation.

“U-um. Hey, Gaster,” Alphys said, apparently noticing his lost look and taking pity on him. “Have, um… have you tried the soda?”

Gaster glanced towards the kitchen table Sans and Papyrus were loading up. “No, I Haven’t.”

“That sugary crap is garbage,” Undyne said. Then she made a face. “Actually, it’s probably better than the food. Don’t eat the lasagna.”

Gaster raised an incredulous eye at the dish on the end of the table. “Is That What That Is?”

“Yeah,” Undyne grimaced. “We’re still working on that one...”

“I’m Beginning to Understand Why Sans Is Always Eating At Grillby’s,” Gaster said.

Undyne puffed a lock of hair out of her eye. “Pff. Buying food is boring. You’ve got to work for it!”

“That Sounds Exhausting,” Gaster noted.

“Hell yeah!” Undyne exclaimed. “What’s a good meal without a good workout?”

Gaster exchanged a look with Alphys, who shrugged helplessly. The two subsided on instant ramen at work.

“hey,” Sans said, joining the group. “did i hear people talkin’ shit about my bro’s cooking?”

“W-what?” Alphys stuttered. “N-no! Of course not! We, u-um…”

“well, that’s good,” Sans said. “anyway, I’ve called Grillby and asked him to bring some burgers over. everything here’s pretty much burnt.”

Gaster snorted. “Everything?”

Sans looked over at the table. “well i guess the soda’s okay…”

Gaster chuckled and Alphys cracked a nervous smile, though Undyne merely sighed. “This is why I wanted to stick with pasta for a few more weeks...”

After that the conversation turned to Undyne and her cooking classes with Papyrus - the latter of whom helpfully interspersed the conversation with demonstrative poses. Gaster sat back and let the chatter happen around him, taking pleasure in just listening to the others talk. Occasionally Sans would jump in to make a terrible pun, but for the most part the smaller skeleton also seemed content to listen. His brother was a dominating presence, and most of the talk took place around him.

“look at you,” Sans nudged Gaster’s side at one point. The others were watching Papyrus display his latest Special Attack. “being all social and stuff. acting normal. and i’ve heard the royal scientist is a humourless workaholic.”

Gaster raised an eyebrow at Sans. “Is That What They Say About Me?”

“well,” Sans considered, “you don’t exactly come off as chummy.”

Gaster smiled wryly, turning his attention back to the other party attendees. A couple of his coworkers had come up to him earlier to mumble brief greetings, but apart from that there’d been very little socializing.

“You Know, Sans,” Gaster said, “I’m Beginning To Think People Find Me Intimidating.”

“ _no_ ,” Sans said. “ _really?_ ”

Gaster smirked at Sans’s poorly concealed smile. “Is The Sarcasm Necessary?”

“what can i say, doc,” Sans shrugged. “you’re not exactly in abundance of _funny bones_ , heh heh.”

“I’m Just Out Of Practice,” Gaster waved it off. “No One Else Tells Jokes To Me.”

Sans shook his head. “you can’t wait for others to initiate, g,” he said. “just throw ‘em out there. you gotta have more of a _backbone_.”

Gaster considered. “I Suppose I Could Attempt To Be More _Humerus_.”

“ayyy,” Sans gave Gaster finger-guns. “now you’re gettin’ it.”

Gaster was trying to come up with another pun - stars, he really was out of practice - when a violent tremor ran through the house, accompanied by a distant _boom_.

The smalltalk paused. “What was that?”

There was more murmuring, then another earthquake shook this house. This one was violent, knocking a picture off the wall and glasses off the table.

“EVERYBODY OUT,” Papyrus called over the quickly rising hubbub of the guests. The party hurriedly filed out into the snow, looking around as other residents of Snowdin stepped outside their houses as well. Aftershocks ran through the ground, shifting snow from roofs.

“gaster,” Sans said, his eyes on the east end of the cavern. “what is _that_?”

A red glow was radiating from the distance. The light flickered, dimmed and grew; the eastern cavern seemed hazy, as if it was beginning to fill with smoke. Distant rumbling continued to shiver through the Underground as the lights of Snowdin flickered, then suddenly went out. Plunged into the abrupt darkness, the red firelight seemed to grow even closer and brighter.

“It’s The Core,” Gaster said, his heart sinking as he watched the distant destruction unfold. “There’s Been An Eruption. The Core Is Melting Down.”

 

 

 

 

**Notes for the Chapter:**

> Alright. Here we go.
> 
> I've been waiting to write this next chapter for a long time now. I absolutely cannot wait :D
> 
> Yet Darker.


	18. Yet Darker

**Summary for the Chapter:**

> In which Sans has a bad time.
> 
>  
> 
> Warnings: If you're someone that minds tags, this is the chapter to mind them.

**Notes for the Chapter:**

> Wow. Wow. 
> 
> I'm sorry this chapter took so much longer to come out, but goodness, this whopper is coming in at 11 thousand words. Twice the length of my next longest chapter! I very nearly split it in half to get an even 20 chapters, but I think it probably deserves to be posted all together. 
> 
> It was incredibly fun and exhausting to write. I hope it's at least a little more fun than exhausting to read.

_Twenty seconds_ , Gaster made a mental note. Perhaps twenty-five.

“Sans.”

Gaster held out his hand to the younger skeleton. “Take Us To The Core.”

Sans looked at Gaster in incomprehension - then surprise. “w-what? you want me to… but i’ve never taken someone else with me before!”

 _An oversight,_ a detached part of Gaster thought. He should have tested that months ago.

“Sans, We Don’t Have Time For This,” Gaster said, grabbing Sans’s wrist. Sans flinched but didn’t pull away. “Quickly, Now! If The Core Is Melting Down Then The Lives of Hotlands Are At Stake. Every Second Matters.”

“but i don’t even know if it will work,” Sans said, beginning to look a little panicked. “what if- what if you don’t-”

“ _Sans_ ,” Gaster demanded. Forty Seconds. “ _Do It._ ”

Sans sucked in a breath, and before Gaster had a chance to steel himself they were wrenched away.

There was brief blackness - the void, the nothingness between spacetime - then he jolted back into reality. It felt as if he’d been dragged through the Underground by his soul, and he placed a hand against his chest as he experienced a brief bout of disorientation. From what Sans had told him, it must have been similar to what the younger skeleton felt when Gaster used his time jumps; Gaster decided he wasn’t particularly fond of it.

“thank god,” Sans breathed as they both came out the other side. Gaster shared the sentiment, though he didn’t have the chance to voice the thought as he became aware of their surroundings.

Dust swirled through the air.

Sans gagged as Gaster raised the front of his shirt to his mouth. Everything was coated in a layer of ash and dust, and cast in shades of angry red. There were screams of monsters coming from somewhere in the labs and smoke was pouring from several gaping holes within the facility. Beneath them the magma roiled, throwing up fits of molten rock and hot, wild winds.

Another explosion from somewhere in the Core rocked the Underground and sent Gaster and Sans diving for cover. It was only this that shocked Gaster from his stupor; _Fifty-five_ _seconds_ , he reminded himself. Already they’d wasted too much time.

“The Lower Terminals, Sans,” Gaster said, pushing himself out of the dust. He tried not to think about which of his colleagues it had been. “How Close Can You Get Us?”

“holy shit,” Sans said, staring at the ruined Core. The labs, strung about like a lattice of precariously hanging Christmas lights, were swaying and groaning from the damage. Several of the key structural supports in the lower levels were noticeably missing, eaten away by the magma. In addition to the suspended labs, many of the facilities that were built into the walls of the volcano’s pit were left exposed, torn open like so many wounds. The cliff-face crumbled away beneath the volcanic rumbling, and the suspended labs swayed and tangled as the magma melted through their supports. The Core seemed to be at the edge of a tipping point.

It took a moment for Sans to find his voice. “it’s... it’s all going to fall in, isn’t it?”

“ _Sans_ ,” Gaster urged. Sixty-six seconds.

“i- we should do a series of smaller shortcuts,” Sans said, finally focusing on Gaster. “in case the way’s… gone.”

Gaster put a hand on Sans’s shoulder. “Do It.”

He didn’t have to be prompted again. They teleported away, appearing somewhere else within the facility. The smoke was even thicker here, muting the intensity of the firelight that licked up the walls. Sans only paused there for a moment before he pulled them away again - this time to a catwalk just outside. The path was swaying, far beneath them the dangerous glow of the volcano. Sans ported them again - and again - and again. Gaster just focused on holding onto Sans, only catching snapshots of what they passed. Smoke - fire - dust - steam - injured and fleeing scientists - he didn’t have time to dwell on any of it. He couldn’t do anything to help them; the best use he could be was to access the terminals and reroute power to the Core’s protective spells - if it wasn’t already too late.

The series of teleportations stopped and Gaster looked up, forcing down the bout of nausea that had accompanied the trip.

“Why Did You Stop,” Gaster said, trying to focus on their surroundings. They were on a catwalk, though judging by the nearby facilities it wasn’t anywhere he recognized. “This Isn’t The Lower Labs.”

“this... this was as far as i could go,” Sans said, stepping away from Gaster to glance over the edge of the walkway. “they’re _gone_ , gaster.”

“Gone?” Gaster repeated. He stood as well, taking hold of the railing as he gathered his bearings. The end of their catwalk protruded out into empty air, twisted and mangled where it bent downwards towards the magma. It took him a moment to realize why he hadn’t recognize the area; the entire lab was missing.

Gaster swore, leaning over the railing.

“careful, doc,” Sans cautioned, stepping back from the edge himself. The cables that had kept the lab aloft were now dangling over the lip of the cliff. Unlike other supports, however, which hung loose and swayed with each heated gust, the cables that had kept the lower terminals strung were still taut. Gaster leaned out a little further.

“It Survived,” he said, gesturing beneath them. Miraculously, the facility had lodged itself on an outcropping halfway down the cliff’s face, still hanging by a handful of cables and exposed wiring.

“no way,” Sans said, shaking his head. Gaster first took it as an exclamation of surprise before Sans quickly clarified himself. “no way you’re going down there.”

“I Have To See If I Can Reactivate Some Of The Barriers,” Gaster said. “Without Protection, We Risk Losing The Whole Core - And Everyone Still In It. I Can Also Shut Down The Generators From There. If The Power Converters Were To Be Swallowed By The Volcano While They Were Still Active...”

Sans swore, understanding the implication all too well. The magical energy contained in the powerplant, if released all at once, would be comparable to that of a bomb. A very powerful bomb.

 _Two Minutes,_ Gaster reminded himself. They needed to move quickly.

“Well?”

“shit.” Sans grit his teeth, grabbed Gaster’s arm, and teleported them down the cliff.

The floor jumped beneath their feet, sagging under the sudden weight. The room was tipped at a forty-five degree angle, causing Gaster to slide more than step down the room towards the terminals. Sans kept back, hanging onto a stray cable for balance.

It was a mess. The roof had caved in on the east terminal, rendering that station completely inoperable. The center and west stations fared better, but not by much. Gaster splayed his hands over the terminals and funneled his magic into the machine. The terminals began to hum as they came online, glowing with the color of his magic. Acting quickly, Gaster sent out several commands - demanding diagnostics, routing energy to the barriers, calling up a display to more quickly diagnose the issues.

Lights sparked in the air before him, then went out. The display wasn’t working. Frustrating, but he could work around it.

The room groaned, and there was a dizzying impression of swaying.

“uh, doc,” Sans called. Gaster didn’t reply. His hands were flying over invisible systems, accessing routines, trying out different paths. Dammit, nothing was working - the whole system was broken down, on both a magical and mechanical level.

“ _doc_ ,” Sans said again. The room shivered. “the cables-”

“Not Now, Sans,” Gaster said, his mind racing. There had to be someway to fix it. If he could just-

“Gaster!” Sans shouted, causing the scientist to jerk away from the terminal. “We gotta get out of here _now!_ ”

Sans let go of his hold on the wire, perhaps anticipating a quick shortcut to Gaster. The floor lurched first, however, causing Sans to lose his footing and go sprawling forward. He tumbled down the floor, impacting one of the terminals with a sickening _crack_.

“ _fuck_ ,” Sans groaned, raising a hand to his head. A paper-thin crack ran from his left temple to the back of his skull. His voice sounded dazed. “oh. am i-”

The floor dropped again, and this time it didn’t catch. There was a wiry twang - a metallic snap - and the lab swung downwards. The world tilted and the wall became the floor as the skeletons were thrown into it. Loose cables and debris assaulted them as the lab grated down the rock wall, snagging and lurching and falling towards the magma. Gaster summoned an array of hands to grab something - anything - for purchase, but the room’s wreckage made it impossible for him to hold anything for more than a moment, let alone keep track of which way was up or down.

Their fall was abruptly arrested as they crashed into a ledge. Spears of rock stabbed through the walls, crumpling the facility like an aluminum can and ripping the floor apart. Metal screeched as the room sagged, half of it clinging to the rock while the other half bent towards the volcanic surface. Heat flooded the room as it was cracked open, shimmering and blisteringly hot from their far-too-close proximity to the magma.

Gaster hooked an arm around a jagged strut, ignoring the bite of the metal in his bones as he struggled to keep from sliding towards the empty air. Sans was also nearby - cinched between one of the broken terminals and half of a collapsed wall. The smaller skeleton moaned, attempting to sit up before finding himself trapped.

“gaster?” he called, turned away from the other scientist.

“I’m Here,” Gaster said. Now that he had a moment to focus, he began to gather his magic. “Hold On, Sans. I’ll Get Us Out Of Here.” The magic pulsed through his bones, throbbing tightly in each of his cracked scars.

“okay,” Sans said, his head falling back against the floor. He didn’t sound good - and the fact that he hadn’t teleported away meant he probably wasn’t doing well either. How much battering could a monster with one health sustain? Gaster forced the thoughts aside. It didn’t matter. He had to focus.

The lab lurched. Hung. Slipped again.

The metal walls shrieked and groaned - they’d break away at any moment. Gaster tried to block it all out and concentrate, summoning as much of his magic as he could. How long had it been? He’d lost count - four minutes at least, which put him over his limit. It didn’t matter - he’d just have to do better, push himself further-

There was a sudden _snap_ and the wall above Sans gave way. Sans jerked at the noise, raising a hand to the falling debris. Blue magic swirled around his hand as the wall froze, stopping it mid-fall. Gaster let out a breath as Sans’s magic held the suspended piece of concrete in place.

Then the light stuttered - went out. And the wall crashed down.

It was sudden - the span of a gasp. One moment Sans was there and the next he wasn’t.

The rubble smashed into the floor and a cloud of white puffed out from Sans’s suddenly empty clothes.

Dust.

Gone.

“ _SA-!_ ”

Gaster bit the word off, forcing himself to look away. No, not now, he couldn’t lose focus now.

“ _Concentrate_ ,” he demanded, unable to keep from replaying the moment that had just burned itself into his mind. Gaster squeezed his eyes shut, as if that would help, and tried to focus instead on the pain of the magic in his scars. _He’d just turned to nothing in the blink of an eye._ Stars, Gaster felt like the magic was going to split him open. _Dust billowing out_. Just a little more. He had to be certain, had to be precise. He could handle a little more… _Any moment now, he’d be dead, too. He’d fall into the volcano. Any second…_

Gaster gripped his magic and _pulled_. With a final metallic screech the lab fell away beneath him even as Gaster wrenched himself out of existence and into the familiar blackness of the void. The magic twisted and burned, a living fire in the nullspace. It was more wild, more powerful than it ever had been before, and it dragged Gaster blindly through the darkness intent upon its destination.

He hoped it would be enough.

Gaster slammed back into reality in Sans and Papyrus’s living room. The sudden change in scenery was almost more shocking than the trip itself; from death and screams to a room full of laughing friends. Gaster sagged backwards as relief and exhaustion flooded through him, luckily finding a wall to slump against. Out of habit he restarted the count - _one, two, three…_

Sans let out a choked scream. Stumbling back into the dining table and sending several plates and drinks crashing to the ground, the party came to an abrupt stop.

“SANS!” Papyrus cried, leaping to his brother’s side. “ARE YOU ALRIGHT?”

Sans had one hand pressed against his chest and the other at his temple, brushing over the spot where the crack had been. His eyes had shrunk to pinpricks of light.

“oh my god,” Sans heaved, looking through his brother. His fist knotted into the front of his shirt as he swayed.

“SANS,” Papryus said, steadying his brother with a hand on each shoulder. “WHAT HAPPENED? ARE YOU HURT? SANS. _SANS!_ ”

A crazed smile twitched onto his face, and Sans’s labored breaths turned into laughter, shaky and broken. “i- i- i- think i _died_ , heh heh.” Sans looked at Papyrus and his smile cracked. “i could feel it, heh heh. oh god, i could _feel_ it, paps. it hit me and then i was - then i was _dust-_ ” Sans choked on the last word as Papyrus enveloped him in a hug. Sans clutched him tightly back, burying his face into his shoulder.

“I DON’T UNDERSTAND WHAT YOU’RE TALKING ABOUT,” Papyrus admitted. “MAYBE IT WAS A BAD DREAM. ERM, DAYDREAM? BUT YOU’RE OKAY NOW. YOU’RE HERE, AND YOU’RE SAFE.”

Sans nodded into Papyrus’s shirt, refusing to pull away. His breaths were fast and shallow - almost verging on a hyperventilation - though the longer he held his brother the more his breathing began to stabilize.

Gaster watched, a sinking feeling growing in his soul as he realized what he’d have to ask of Sans. Not yet, however. He’d give the brothers some time - he could do that much for them. And if he were being honest, he still needed a few more moments to recover himself. He’d gone back at least five minutes. It was nearly double to longest time jump he’d managed before, and Gaster was doubtful he’d ever be able to pull a stunt like that again.

A faint _boom_ shook the house.

“What was that?”

The monsters that had previously been watching the brothers’ perplexing embrace now shuffled uneasily, looking around for the source of the sound. Sans was slow to relinquish his grip on his brother.

“sorry, bro,” he said. Tears hung in the corners of his eyes and he was trembling slightly, but his voice was now quiet and steady once more. “i didn’t mean to scare you.”

“I AM JUST GLAD YOU ARE OKAY,” Papyrus said, relief plain on his face.

“yeah,” Sans said, slowly looking away from his brother. It didn’t take him long to catch sight of Gaster, resting against the wall. “yeah. i’m okay.”

The second explosion rocked the house, causing Sans to flinch.

“you... better get everyone outside,” Sans said to Papyrus. His brother frowned slightly, giving his brother a curious look, but after a moment of hesitation he stood up and began shepherding people out of the house. Sans stayed where he was, looking down at his feet.

“...Are You Alright?” Gaster finally ventured.

Sans shrugged. “i dunno. i guess so.” He let out a heavy sigh, sticking his hands in his pockets. “it just… i mean... i... i really died, didn’t i?”

“Yes,” Gaster said softly. “I’m Sorry.”

“and you brought me back,” Sans said, a statement more than a question.

Gaster didn’t have to answer.

“...thanks.”

“I’m Sorry, Sans,” Gaster grimaced. “I Should Have Listened When You Were Trying To Get Me To Leave - I Should Have Jumped Us Back Sooner. I Should Have… Acted...”

“it... doesn’t matter,” Sans let out a breath. “it’s like… it’s like it never happened, right?” Sans smiled wearily. “no skin off my nose. heh.”

The attempted levity did nothing to make Gaster feel better about any of it. In fact, Gaster found himself slightly disturbed by Sans’s easy dismissal of the event as if it had never happened. But that was a conversation for a different time.

“You Know,” Gaster forced himself to say, “We Still Need To Go Back. We Still Have To Stop It.”

Sans looked up at Gaster, who was surprised to see not distress on his assistant’s face, but resignation.

“i know,” he said.

“WHERE… WHERE ARE YOU GOING?”

Papyrus stood in the doorway, looking between Gaster and his brother. The other monsters had already filed outside; only the skeletons were left standing in the empty house. They both avoided his eyes.

“The Core Is Melting Down,” Gaster said when Sans didn’t answer. As if to punctuate his words, the third tremor came and the lights flickered out. “We Can Fix It.”

“THAT SOUNDS DANGEROUS,” Papyrus said, again looking towards his brother.

“we’ll be okay,” Sans said. He didn’t sound very convincing, Gaster noticed. Papyrus did as well.

“IT DOES NOT SOUND AS IF YOU WANT TO GO.”

“we gotta, paps,” Sans sighed. Then he looked at Gaster. “…if it’s not too late?”

“I’ll Take Us Back To Buy More Time, First,” Gaster said. “Just A Minute Or So. I Can Manage That Much.”

“right.” Sans rubbed his head. “yeah, of course.” Sans glanced back towards his brother, and Gaster knew what he must be thinking. Papyrus wouldn’t even remember this conversation.

“I WILL COME, TOO,” Papyrus announced, though Sans was already shaking his head. “I CAN HELP!”

“i don’t want you to get hurt,” Sans said. “i can’t risk that.”

Papyrus scoffed. “THAT IS EXACTLY WHY I SHOULD GO! I DO NOT WANT YOU TO GET HURT, EITHER.”

“papyrus,” Sans pleaded. “you can’t. please. it’s dangerous, and…” he trailed off, unable to think of a better excuse.

“...And It Would Take Too Much Time To Explain,” Gaster supplied. “Speaking Of Time, I Don’t Think We Should Wait Much Longer.”

“right - sorry,” Sans said. “paps, we gotta go.”

Papyrus looked upset and as if he wanted to argue more. Something in his brother’s voice stopped him, however. Instead, he crossed the room and knelt down before Sans.

“YOU’LL BE CAREFUL?” he asked.

“of course, bro,” Sans said. “i’ll be fine, i prom-” Sans stopped himself before he could complete the sentence.

“PROMISE,” Papyrus urged, keenly aware of what his brother had been unable to say. “PROMISE YOU’ll BE OKAY!”

Sans gave him a pained look. How could he make that promise knowing that he had just died - and it was not only possible but likely it could happen again? Papyrus couldn’t have known, but it wasn’t fair to ask something like this of his brother. Sans was silent for a few moments, and Gaster was about to prompt him once more before he finally spoke.

“okay,” Sans said, his voice so low it was barely above a whisper. The skeleton reached out a hand and squeezed his brother’s shoulder. “i promise i’ll be careful, papyrus. gaster?” he added before his brother could reply, and it was all the cue Gaster needed to activate the magic he’d been readying. “i’m ready. let’s-”

By the time the word “go” left Sans’s mouth, the scene had changed. The lights were on, the party was ongoing, and the meltdown had yet to start.

Unlike the previous jump, this one almost felt pleasant in comparison. A little twinge in his bones, but it was nothing like the longer jump.

“Ready?” Gaster asked Sans, who was shaking off the disorientation. “We Have Less Than A Minute.”

Sans grabbed Gaster’s sleeve in response, wasting no time in teleporting them directly to the lower terminals.

The room was empty and whole, though out the windows the telltale signs of the active volcano were more than apparent. Gaster crossed quickly to the terminals, attempting to ignore the fits of magma that were being thrown into the air outside. Using his magic to bring up the terminals’ displays, he quickly began to sort through the diagnostics. Behind him, Sans nervously cleared his throat.

“i’m gunna go sound the evacuation,” he said. “even if you get the shields up, it’s still pretty dangerous to be around the core when it’s like this.”

Gaster entered a few more commands. “Good Thinking,” he said, late to respond. Several sets of hands were flying over the consoles, which took an abundance of concentration to maintain and direct. “Go Do That. Let Me Know When…” he trailed off as there came a small pulse of blue light and breath of wind; Sans had already teleported away. Good, with them multitasking they could get more done.

Oh, right.

And probably, Gaster belatedly realized, Sans hadn’t wanted to hang around the room where he’d just died. Well, there was little Gaster could do to help with that. Getting pulled back from death probably wasn’t something one could just walk off, no matter how indifferent Sans appeared to be acting. Again, Gaster reminded himself he would have to speak with Sans about that later.

A low, electronic wail rose through the Underground, signaling Sans had activated the evacuation alarm.

Gaster gave a start, refocusing his attention on the task at hand. How long had he been here? Too long, probably. The generators, at least, had been an easy fix. Rerouting power to the backup cells deeper in Hotlands, the Core’s power plant was now dormant and posed no threat should it be overcome by the magma. The shields, however, were a different story.

All the protective spells were down. Gaster didn’t understand how this could have happened, as they were supposed to be kept running at all times. They operated on a power source independent from the Core - refreshed by Gaster and a crew of magically adept scientists on a regular basis - and should only be able to be turned off manually. Turning them on again was no easy chore either; he had to reset each of the shields individually, and he wasn’t even halfway through the list.

But how had this _happened_ ? How could someone have accidentally turned off not one, but _all_ the protective spells?

Unless… it wasn’t an accident.

A plume of magma erupted nearby, filling the room with an intense, red haze as the lab was buffeted by a pyroclastic surge. Gaster stumbled away from the terminal as the room swung, catching himself with his constructs. The lab managed to hold together, protecting Gaster from the elements, but molten rock rained down on the roof in a menacing patter. The supports groaned, and Gaster heard a familiar, wiry _snap_.

It was time to go.

Gaster made for the exit, staggering as the room swung beneath his feet. Throwing the door open, Gaster clutched the frame as he was met with a dizzying sense of vertigo. The catwalk that led to the lab’s entrance appeared to be swaying back and forth before him, an illusion caused by his own moving reference frame. There was another snap and the room jolted, tilting slightly away from the catwalk. Damn it all! He would have to jump. But could he make it?

Gaster was all too aware of the cables creaking above him as he waited and tried to time the jump. Just… another… moment...

Another eruption collided with the lab. Gaster lost his hold - saw the world spin and fill with fire - there was an impact - a lurch in his gut - then a flash of blue as something wrapped around his waist -

Gaster and Sans stumbled onto one of the Core’s clay paths. Gaster clutched at a nearby railing as a screech of metal cut through the air; one level below them several more wires snapped and the lower terminals fell, swinging out of sight. There was a muted impact when the lab crashing into the side of the cliff, finding its precarious resting place halfway down the rock wall.

Gaster let out a breath. “Thank You, Sans.”

The smaller skeleton gave a nervous, breathy laugh. “jeez, you like to cut it close,” Sans said. “guess that makes us even. did you fix it?”

Reluctantly, Gaster shook his head. “I Was Able To Power Down The Core, But I Wasn’t Able To Bring All The Shields Up In Time. We Should Avoid A Catastrophic Failure, But May Lose Some Of The Lower Labs. Levels One Through Three Should Be Safe, At Least.”

“and the basements?” Sans asked. “there’s still monsters down there. do the elevators have power?”

“Yes,” Gaster said, though a wave of uncertainty quickly passed over his face. “But It Won’t Be Swift Enough To Take All Of Them. Most Would Have To Wait, Or Use The Stairs…”

Sans looked at Gaster in horror, then both their gazes turned down towards the lower levels. Magma was melting through the catwalks, splashing against the exposed labs, paths, and switchbacks. Labs hung adrift, crashed into cliff walls and each other; too many routes terminated in dead ends, too many paths had become treacherous. Without help, the monsters in those lower levels would surely perish.

“can you go back?” Sans asked. “could you restore the magic to those levels, too?”

Gaster grimaced, rubbing at the crack in his skull. “I Don’t Think So. I Did What I Could In The Time That I Had. The Only Thing I Could Change Would Be Which Spells To Turn Back On, And Which To Leave Off.”

“then we just gotta deal with what we’ve got,” Sans said. He held a hand out to Gaster, and the Doctor took it. Wasting no time, the skeletons vanished.

They reappeared in one of the lower labs. The first one they arrived in was broken - partly melted through along the north wall - but empty. Gaster glanced quickly around the area to ensure they hadn’t missed anything, then nodded to Sans. The smaller skeleton teleported them away once more, hopping to a nearby lab. The second and third were empty as well, though their arrival was met with a couple of startle cries in the fourth lab. The monsters that had been huddling in the room jumped at the sudden company, though their surprise was quickly overcome by fear once more.

“Doctor Gaster!” The monsters ran over to them. Inside, the evacuation alarm reached a echoing, deafening blare and the monsters practically had to yell to be heard. “We’re trapped! The walkways are too dangerous-”

“You Can’t Stay Here, Either,” Gaster interrupted. “The Shields Are Down. Sans, Can You Take Them?”

Uncertainty passed over Sans’s face. Teleporting ten other monsters was very different than one. “i dunno, doc, this is all new to me. one at a time, maybe, but more than that…” The room lurched, metallic groans shivering through the structure.

“No Time,” Gaster decided. “Out!” He led the rush to the door, summoning an array of bones along the way. Sans trailed after the end of the group, following Gaster’s lead and summoning his own wave of bones.

The heat hit them like a furnace, causing several of the monsters to gasp. Gaster gestured and his constructs fanned out above the group, forming a makeshift barrier over the scientists to stop any falling debris. Catching on Sans added his bones to the mix, constructing a wall closest to the active volcano as well. The group fled, making a mad dash over the earthen pathway to the next nearest lab. It was a long, winding route to the closest set of stairs or elevator.

“gaster,” Sans said, teleporting to the front to run alongside the royal scientist. “there’s so many other rooms…” Unable to match Gaster’s pace as he began to fall behind, Sans blinked a few steps ahead. “...can we keep this up?”

“I Don’t Know,” Gaster admitted. “But We Have To Try.”

They burst through the doors into the next lab, the coolness a welcome relief. They were left little time to relax, however, as it became obvious their exit - a passage leading to the next lab - was blocked by a large and crumpled duct.

Without breaking stride Gaster sent his bone constructs to wedge themselves beneath the pipe, slowly straining to leverage the equipment out of the way. Sans’s blue magic joined Gaster’s bones a moment later, and the tension abruptly lifted. Gaster glanced at his companion in mild surprise as Sans tossed the duct aside, his eyes burning with blue magic. While it was certainly within the known limits of what Gaster had witnessed Sans lift, the ease with which he had done so caught Gaster off guard. Just another one of Sans’s abilities that Gaster had never truly explored. He should have known by now to stop underestimating what Sans was capable of.

The group filed into the next lab, where they picked up a few more scientists that had been taking shelter in the room. From there it was a series of desperate dashes between buildings, catwalks, and crumbling pathways. It would be a miracle, Gaster thought, if they made it through without losing anyone.

Even as the thought passed through his skull a wave of magma reared up, splashing across their path. Gaster skidded to a halt, catching himself with several hand constructs as the catwalk began to dissolve before him. A spray of molten rocks rained down on top him, striking the bones he’d cast overhead. The constructs cracked - and several vanished - under the fierce heat, and several small beads of slag wormed through the gaps in his defense, striking Gaster. The rocks burned through his coat and seared into his chest and forearms, carving grooves into his bones before the molten gravel fell away. Gaster hissed in pain, jerking his constructs instinctively closer as he felt his health dip.

“Back!” he shouted to the group that was pressing up against him. “Quickly! Turn Back!” The bridge began to sag downwards as the monsters backpedaled. Melted through from the magma, one of the suspension wires snapped and sprang away - Gaster made a mad grab toward the cable, barely catching it with one of his hand constructs. Summoning a dozen more, he took hold of both the cable and the walkway as he backed up, struggling to reunite the pieces. Blue magic lifted the ground beneath his feet a moment later, and Gaster quickly knotted the cable through the handrail before letting his magic dissolve as he stumbled onto more solid ground.

“we should cut back through the stationary labs,” Sans said before Gaster could thank him. “it’s too dangerous out here.”

“It Won’t Be Much Better Inside,” Gaster said, catching his breath. Running a hand over his burned torso, he tried to still the panic that had briefly spiked through him. It was easier to focus on the pain. “Perhaps More Treacherous. We Could Make For The Eastern Elevator, But That Path Will Bring Us Down And Even Closer To The Volcanic Surface.”

Sans only then seemed to notice Gaster’s injury. The magic in his eyes flickered out as they were overcome by concern. “hey, woah, are you alr-”

“It’s Superficial,” Gaster cut him off. “I’ll Deal With It Later. For Now, We Need To Keep Moving.” He glanced towards the stationary labs, carved into the volcanic walls of the cliff. “But Perhaps You’re Right. It May Be Best To Retreat To The Main Labs For Now.” Gaster turned and led them back towards the buildings, leaving Sans little time to interject. The last thing he needed was for his assistant to be worrying over him; they had to keep a sharp focus on the task at hand. Afterall, Gaster could manage a handful of rocks - it was his temporal magic that was doing the real damage to his health.

Inside wasn’t much better. The volcano’s tremors had knocked everything to the floor that wasn’t rooted to a surface, and a handful of things that were besides. The earthquakes had also shifted the rock wall, half caving in some rooms, and merely bowing the structural supports of others.

Even so, the first several rooms they passed through instilled a new confidence in the group of scientists Gaster and Sans had collected. Out of the heat, out of sight of the volcano, it was easier to think that they were safe. This briefly sustained courage was dashed away, however, when a gash in one of the walls - vomiting a deadly heat into the room - provided an all-too-pertinent reminder that it was only a tenuous layer of metal that separated them from quick, fiery death.

Now that they had some direction, the scientists ran ahead. Gaster let them pass, falling to the back of the line with Sans, who didn’t appear to be handling the exercise well. Beads of blue magic had manifested on his skull and were running down his cheeks in some futile attempt to cool him off. With any other monster Gaster would have been concerned by the amount of magic he was losing, but Sans, as he knew, was a special case.

The passages were empty of other monsters, which Gaster took as a good sign. By now, they’d all likely made it to the elevators and stairwell which, with luck, they would be coming upon soon. Good. If the way was clear, then Sans and Gaster’s path would just be easier the next them they-

One of the monsters let out a cry, causing the rest of the group to stumble to a halt.

“What Is It?” Gaster called, trying to peer over the heads of the scientists. Sans blinked away, and Gaster heard a muted “you okay?” There were more mumblings, and by the time Gaster made it to the front of the pack he realized the cry had been made out of distress rather than pain.

Rubble blocked the entryway to the hall which housed the stairs and elevator, but it was the base of the door that the monsters were looking at. There, scattered out beneath the wreckage, was an empty set of clothes and a pile of white dust.

“Th-that shirt,” one of the monsters stuttered, clearly shaken. “Birdy has one just like it. Y-you don’t think…”

“Poor Thing,” Gaster muttered. “Must Have Been Caught In The Collapse. Sans,” he said in the same breath, gesturing towards the door. “Help Me Clear This Out.”

Sans looked at him in disbelief, then frustration. “seriously?” He threw a pointed hand back towards the shaking scientist.  “jeez, i keep forgetting how much you suck at this. can’t you give her a minute to-”

“No, I Can’t,” Gaster snapped, summoning hand constructs as he began to test the rubble that blocked the door. “I Know Your Trust Is Not Something I Have At This Moment, But You’re Just Going To Have To Trust That I Have A Plan.”

Sans glared at him. “and being an asshole is part of that plan?”

“ _Dammit, Sans_ ,” Gaster swore, causing the smaller skeleton to flinch in surprise. Gaster gave up prodding at the door and summoned several bones to cathartically stab through the blockage instead. “For God’s Sake, We’ll Go Back And Save This Monster! But Time Is Still Of The Essence - Stars, You Need To Stop Thinking So _Linearly_. We Have To Make The Most Of What Time We Have, Instead Of Wasting It Arguing Over Something That Won’t Even Happen If We Do This Right. And By My Calculations, I’ve Got About Thirty More Seconds Before We Begin To Push My Limits.”

There was a pause, then a few moments later several more bones manifested and jutted into the rubble alongside Gaster’s. Blue magic seeped around the edges of the debris, slowly jostling them out of place as the bones crumbled the larger pieces apart.

“sorry,” Sans mumbled. “i know you can just undo it all, but it’s hard to not get caught up in the moment. someone died there, and i can’t just stop caring, ya know?” The bigger pieces broke apart and Sans forced them out of the opening.

“It’s Not About Not Caring,” Gaster said, focusing his efforts on widening the hole. “It’s About Not Letting Your Emotions Disrupt Your Judgement. You Can Care And Stay Focused At The Same Time. Caring Is A Good Motivation In Making Sure You Achieve Your Goals.” Sans helped Gaster with the last of the rubble, clearing enough space for them to step through the doorway.

Sans offered a weak laugh. “sorry. i know. you’re right. guess i got pretty _heated_.”

Though the atmosphere in no way lent itself to humor, Gaster found a hint of respite in the pun. It was a peace offering, of sorts. In spite of himself, Gaster quirked a small smile. “Yes. You Were Acting Rather _Hot Headed_ , Weren’t You?”

Sans chuckled wearily, stepping through the door. “hope that doesn’t mean you’re going to _fire_ me when…” Sans’s voice drifted off.

“Sans?” Gaster prompted, his smile fading. His assistant didn’t answer, and as Gaster followed him through the doorway it became clear why.

The hall was a mass grave. Every surface was covered in a layer of white dust, the floors so liberally and uniformly coated that it was impossible to tell where one monster had ended and another began. The roof stretched higher than it should have, exposing loose circuitry and dripping pipes where the plaster had been ripped away.

The ceiling had collapsed, burying everything on the floor below it. Out of the corner of his eyes Gaster saw Sans sink down to his knees. Perhaps his assistant cared a little _too_ much; it would destroy him if he let it. Despite what he’d just said, Gaster found apathy a more effective coping mechanism, and was trying his hardest not to dwell on what had taken place.

Trying not to imagine what the last few moments of these monsters had been like.

Behind him, the scientists gasped as they caught sight of the carnage. One began to cry, and Gaster slowly shook his head.

“Time’s Up,” he said to himself, gathering his magic. The way it flooded through his marrow and stretched at his scars was a welcome distraction. He let the pressure build, purple magic flooding the cracks in his bones as they were painfully stretched, waiting until the pain was almost too much until-

\- he took them back.

Gaster and Sans were standing on one of the volcano’s ledges just after the lower terminals had broken free and swung out of view. It wasn’t quite as far back as Gaster had hoped to take them - there would be no more attempts to change the terminal settings now - but he thought it would be enough.

Sans groaned, clasping his hands behind his neck as he tilted his head back and let out a sigh.

“Are You Alright?” Gaster asked, rubbing at the cracks in his radius.

“i feel sick,” Sans admitted. “it’s just… so much death.”

“I’m Sorry,” Gaster said, doubly so knowing he couldn’t let Sans leave, as much as he wanted to. Without Sans, Gaster’s abilities were significantly diminished. Even with time travel on his side, he wouldn’t be able to cover the whole Core on his own - not, at least, before his magic ran out. No, they could only save everyone together.

“We’ll Head Down To The Elevators First This Time,” Gaster said. “See If We Can Get Everyone Out Of There.”

“yeah,” Sans said, letting his arms fall back to his side. “alright.” He held a hand out for Gaster, then curled it back as a thought struck him. “what about the first group of scientists we ran into - they’re still in the suspended labs.”

“We’ll Have To Come Back For Them Next Time,” Gaster said. “Once We Have A Better Understanding Of When Everything Takes Place.”

Dismay crept slowly over his face. “we’re letting them die,” Sans realized.

Gaster had hoped Sans wouldn’t dwell on it too much. “In This Timeline,” Gaster admitted. “Yes.”

“and how many times are we…” Sans trailed off, slowly shaking his head. “no... i understand. as many times as it takes, right?”

Gaster merely gave a stiff nod.

“okay.” His sigh was heavy, but he extended his hand back out for Gaster. “okay. let’s go, then.”

They teleported directly to the elevator.

The room was filling with monsters, more still arriving even as Gaster and Sans appeared. A group had formed nearest the elevator, though these were beginning to trickle away and form another cluster near the stairwell, which appeared to be too overcrowded to be making progress.

“the elevator’s broke,” Sans noticed. Its doors stood open, lights sparking from within.

“And There’s Too Many For All To Take The Stairs,” Gaster agreed. “We’ll Have To Get Them To Retreat - Find A Different Way.”

A quake rocked the room, and the lights flickered. The ceiling shuddered, releasing a snowfall of dusty plaster. Sans and Gaster exchanged a look.

“EVERYONE,” Gaster called, attempting to yell over the din of the panicked monsters. A few nearest to him turned to his voice. “YOU ALL MUST LEAVE THIS VICINITY! THE ROOF IS ABOUT TO CAVE IN - GET BACK INTO THE HALL. QUICKLY, NOW!”

Gaster cleared his throat and stepped aside as many of the monsters followed his advice, heading back towards the hallway instead. Stars, he wasn’t accustomed to speaking so loudly - he had no idea how Papyrus managed it.

They weren’t moving fast enough, however. In fact, there were a handful of monsters that were still trying to get _into_ the room, which was causing the doorway to jam up. Lord, he’d just made it worse - now both exits were blocked.

“Sans,” Gaster said, turning to the smaller skeleton. “You’ll Have To Get Them Out. One By One If Need Be.”

Sans nodded, vanishing in a pulse of magic. In the meantime, Gaster decided he’d have to make a different exit. Summoning a blaster, Gaster aimed it at a wall. Hopefully there were no monsters on the other side - and if there were, then he’d just have to live with it and do better the next time around.

Gaster let loose a beam of energy, blasting a hole out into the nearby hallway. Cracks spider webbed away from the crater, creeping dangerously close to the ceiling, which shifted beneath the impact. Without waiting, Gaster turned to a different spot - allowing space for the monsters to begin to run through - and repeated the process. There were flashes of blue where Sans was teleporting, grabbing monsters one at a time and removing them from the premise, but it wasn’t happening nearly as quickly as Gaster had hoped.

Only half of the monsters had managed to escape when the ceiling began to crack. Sans and Gaster stopped, looking up. This was it. They’d moved as quickly as they could, but it wasn’t enough. If they tried again, could they do anything better? It didn’t matter - it was time for them to leave.

“Sans,” Gaster called. The skeleton glanced back at him, then turned his attention back to the ceiling. Gaster frowned. What was he thinking? They had to leave now, before they were buried with the rest of the monsters. “Sans!” Gaster called again. “Get Us Out Of Here.”

“just a minute, doc,” Sans said, far too calm given the circumstances. An array of bones appeared around Sans, then sprang towards the ceiling, growing until they spanned the height of the room. The constructs stabbed into the surface, bracing against the roof.

Gaster gaped. Did Sans really think he could save the monsters left in here? It was absurd! He was going to get them both killed! Gaster swore, turning a blaster towards the nearest space of open wall. At the very least he could get himself out - turn back time should the worst happen, as he expected it would. He didn’t want to leave Sans to die - again - but he could at least guarantee it wouldn’t be permanent. Gaster blasted an opening through the wall at the same time another quake hit, and the ceiling began to crumble.

The shaking knocked Gaster off his feet and the roof from its foundation. Like cracks of lightning, giant crevices snapped up the walls and across the ceiling, fracturing the drywall and structural supports alike. The ceiling gave around Sans’s bones, sagging down for a moment before breaking off altogether. Gaster frantically began to gather his magic, but it wouldn’t be enough - not nearly enough time -

Twenty blasters appeared around Sans, each of their maws pointed upwards. They fired as one, vaporizing the rubble they passed through. The room flashed white from the sudden display of raw magic, blinding Gaster before he could look away. There was a rush of wind from the detonation, debris stinging his exposed bones as he was peppered by a violent spray of crumbling plaster. The light died and Gaster’s vision was slow to return - seconds had passed, and it was with no small amount of surprised that Gaster realized he wasn’t dead.

A blue haze was the first thing he was able to see. It was everywhere - above, before, beside - filling the room with cerulean light. Gaster had to blink several times before he could make out what he was seeing, squinting through the cloud of artificial dust.

Not all of the ceiling had been blown away by Sans’s blasters; roughly half, in fact, had still fallen, though none had made it to the ground. Giant slabs of concrete and metal struts hung in the air, wrapped in wisps of fiery blue magic. The pieces rotated slowly, suspended only a few spans above the monsters’ heads. Sans stood on the middle of it all, burning with magic as he held his hands above his head, his skull bowed beneath the weight. Slowly, carefully, he lowered his arms and the debris followed suit. Monsters scrambled out of the way - Gaster among them - as chunks of the ceiling settled on the ground with strained groans. The blue flickered out all at once, and Sans sagged forward, letting out an exhausted breath his must have been holding. It took Gaster a few moments to pick his way across the rubble and reach his assistant.

Hearing his approach, Sans looked up at Gaster with a weary smile - the first genuine smile he’d had since they’d arrived at the Core. “told ya i’d just be a minute, doc.”

Gaster shook his head in relief - or possibly, disbelief. “I Don’t Know What To Say. That Was… Incredible.”

And truly, it was. Gaster had never seen such an awesome display of magic. He’d summoned _twenty_ blasters at once? While simultaneously holding several tons of material in place with only his magic? Sans was quite possibly the most powerful monster in the whole Underground - no, he was certain of it.

“stop, g, you’re gunna make me blush,” Sans teased. The mirth in his smile didn’t linger long, however. “so, uh, guess now we know how to clear this room. just... a thousand more to go, heh.” He tilted his head at Gaster. “where next?”

“Back,” Gaster said, preparing his magic once more. “Always Back.”

 

\---

 

They went back again, and again, and again. Gaster’s magic drained with each jump, and each time they slipped a little bit more into the future, unable to reach quite as far back. They saved the elevator room dozens - maybe hundreds - of times. They went back for the scientists in the suspended labs just as many, until they moved past that point in time and were forced to live with the state of things as they were.

They had everything down to, well, a science. Perhaps no more than ten minutes had passed in real time, but from the skeletons’ reference frame they had been fighting the slow decay of the Core for hours. Every room had been visited - every pile of dust had been addressed. Yet it still felt like each time they went back their actions changed something small, caused some slight ripple, that would prevented their reruns from ever being exactly predictable. It was exhausting work, physically and mentally.

Their magic stores were nearly depleted. Though Gaster’s potential was far less than Sans - so theoretically, Sans should be faring better - it ended up being the smaller skeleton that did most of the legwork. Frequently Sans enacted astonishing amounts of magic that Gaster had no doubt more than exceeded every drop of magic he could possibly pool together - and he didn’t do it once, but over and over again. Gaster lost count of how many times Sans saved their lives.

Gaster was nearly ready to call it a day. He wasn’t sure he’d be able to do another large time jump, and even small ones were beginning to press his luck. Perhaps one last sweep and he’d be satisfied that they’d saved everyone - to their knowledge, at least. He _hoped_ they’d saved everyone. He wanted to believe it. How would Sans fare if, days later, they learned one of their colleagues had never gone home?

A clattering against the catwalk caused Gaster to spin around. Sans had fallen to the ground, his fingers curling through the grate as he attempted to push himself back up. His movements were weak and his bones shook from the effort - Gaster rushed to his side.

“sorry,” Sans panted, accepting Gaster’s hand as he helped him up. “guess i’m… _bone tired_ , heh.” His laugh turned into a gasp, and even once he was on his feet it seemed as if he’d fall down again without Gaster’s support. It was mildly absurd, Gaster thought, that Sans was still even trying to make puns.

“It’s Fine, Sans,” Gaster said. “I Shouldn’t Have Pushed You This Far. You’ve Done More Than Enough.”

Sans nodded, opting not to speak this time as he tried to catch his breath. After several drawn out seconds, he let go of Gaster to brace himself against a small length of railing that still remained on the half-melted bridge.

“Do You Still Have Enough Magic To Teleport?” Gaster asked.

Sans wearily nodded. “yeah. still got some magic. ‘s all this exercise that’s killin’ me.”

“Good,” Gaster said. “Then You Should Go Home. I'll Be Doing The Same Once I've Finished Here.”

Despite his exhaustion, Sans managed to give Gaster a skeptical look. “i’m not leaving you here on your own. it’s too dangerous, g, you know that.” Gaster must not have looked convinced, as Sans continued to press. “just one last sweep. i can manage that. then we both get the hell out of here.”

Gaster was considering this as another quake shook the Underground and a burst of magma sprayed the far end of their bridge. The catwalk swayed from the earthquake, then snapped where the heat had weakened it. Their end of the bridge held, but lurched, sending the skeletons stumbling as the floor swung beneath them. Sans clutched tightly to his rail and Gaster reached out behind him to find one of his own - but his hand met no resistance. Too late in realizing that the guard was no longer there, Gaster’s momentum carried his step backward, past the lip of the bridge, and into empty air.

The world tipped and he was falling. His soul leapt in his chest as hot wind rushed past him, and Gaster experienced a moment of unadulterated panic before he had the wits to grab for his magic. He gathered the energy - as quickly as he could - hastily directing it to perform another time jump. Hardly waiting for his reserves to pool at all, he pulled on the magic, left the present, and snapped back in time.

But he was still falling.

It was the moment after he’d gone over the edge, the moment after his foot had left the platform - he was almost within arm’s reach of the bridge - but it was still _the moment after._

In a state of shock, Gaster realized he had missed.

Maybe his magic reserves had been lower than he’d thought. Maybe he hadn’t allowed himself enough time - or concentration - to properly execute the jump. Whatever the reason it didn’t matter, because the moment he’d botched the time jump was the moment he’d sealed his fate. He couldn’t jump over a previous jump. No matter how hard he might try, he wouldn’t be able to go back to a time before he’d fallen.

So this was it.

This was how it would end.

After everything he’d done - after everything he and Sans had faced - it all came down to the smallest of missteps. He might have found it a little funny if he wasn’t still in shock - or perhaps it was the shock that made the idea seem funny.

_He was going to die._

Gaster wondered how long it would take. He was several stories up, but gravity would make quick work of that. Manically, his mind tried to grasp at a calculation. Only a couple of seconds, maybe-

Pain lanced through his chest as his soul was nearly ripped from his rib cage. Gaster gasped as his vision swam, blue light shining through a haze of unbidden tears. Blue - blue light. He knew that color.

Though he couldn’t see Sans, he knew his friend must have stopped him. Stars, thank god for Sans. What had Gaster done all these years without him? The resurgence of relief, however, was short-lived as Gaster felt the magic waver, and his position in the air slip lower.

Of course. Sans was nearly out of magic as well. He’d managed to arrest Gaster’s fall, but did he have enough to pull him back up?

His question was answered in the next moment as the magic strained - snapped - and left Gaster falling once more. Before Gaster had a chance to even comprehend this development Sans was suddenly in the air above him. Gaster reached out a hand as Sans swiped for it - and missed. The two separated as Gaster fell faster than Sans, due to, Gaster realized, the disparity in their mass. Sans must have realized this as well, for in another flash of blue he had vanished. Somehow, his disappearance left Gaster with a sense of relief. It was too dangerous, he distantly thought, for a skeleton of such low health to be trying to-

Something solid abruptly pressed against his back. Arms wrapped around his waist, there was a flash of blue - a jarring impact - a _crunch_ \- a blossom of pain along the back of his skull -

And solid ground beneath him. Gaster gasped, rolling to his side. They were back on the first level of the Core, on an earth pathway some safe distance away from where the volcano was still roiling.

 _Stars, Sans was smart,_ Gaster founding himself grinning. Sans was so smart. Realizing he’d never be able to catch up with Gaster from above, he must have teleported himself beneath Gater instead.

 _Beneath him_. The words were slow to sink in. Beneath him.

Gaster sucked in a breath, wiping around with mounting horror as he took sight of what - or rather who - had broken his fall.

It was bad. It was very, very bad.

Wide, dark cracks covered every inch of exposed bone on Sans’s body. Even as he watched a thick, red liquid began to ooze out between the fractures, and the front of his shirt began to stain red. There were lights still in his eyes, but every few moments they guttered out, the time between them flickering back on was growing ever longer. Sans was breathing slow and labored, and had made no attempt to move.

“Sans?” Gaster said, reaching a hand out before nervously drawing it back, too afraid to touch him in such a fragile state. “Sans, Can You Hear Me?”

“mm,” the skeleton mumbled, his eyes stuttering back into view. A pained smile spread across his face. “hey. g. caught ya.”

A strange, intangible pain twinged sharply in Gaster’s soul. “You Did. You Did. Sans, You’re Hurt. I- I’m Going To Find Someone To Heal You-” He looked up then, as if expecting to find such a person standing before them. But of course, they were alone. “Oh, Stars, Sans. You’re- You’ll Be Okay.”

Blood bubbled up as Sans laughed weakly, like Gaster had just told the best joke he’d heard all night. Sluggishly, Sans brought a hand up to knock against Gaster’s arm, getting his attention. He was so light, Gaster thought. Sans barely felt tangible at all.

“‘s okay. ‘s okay.” Sans took a long moment to blink. “i... was gunna say something.”

Gaster swallowed hard, looking down helplessly at the small, broken skeleton as he was overcome with a wave of grief and frustration. Why couldn’t he do anything useful? Why couldn’t he have healing abilities? All he had were these damned, useless, temporal powers, not even good enough to stop him from falling off a ledge. They couldn’t save the human child. They couldn’t save himself. They couldn’t even save…

Gaster paused, looking down at Sans as an idea washed over him. The skeleton had noticed the blood on his hand, at that point, which caused another weak chuckle.

“look, doc.” Somehow, his eyes still seemed to dance with amusement. “guess... guess i still bleed. heh heh. ain’t that… a joke…” As they both watched, one of the fissures in his fingers cracked a little more, splitting all the way through the bone. The tip of his finger crumbled quietly away in a gentle fall of dust. “...oh…” Sans sighed.

Gaster looked down at his own hands. It was suicide. But perhaps his magic could save someone after all.

“Sans,” Gaster said, calling upon his dangerously low reserves of magic. He distantly wondered what would happen if he completely drained them - what would happen to his body without anything to hold it together.

“Sans,” Gaster said again when his friend didn’t answer. (Friend? Yes, of course he was. He always had been.) This was the moment when he was supposed to say something profound. When he was supposed to say something clever and memorable. But Gaster didn’t know what to say, and he wasn’t even sure Sans was capable of listening anymore.

“...Do Better Than Me,” Gaster sighed, and activated his magic.

There was the brief glimpse of the void, then he was falling once more.

This time he didn’t feel shock. There was, perhaps, a lingering sense of fear, knowing what was to come, but this was mostly overshadowed by… relief. Satisfaction. Sans was okay, and that was because of Gaster. He wouldn’t let his friend sacrifice himself - not for someone like him. This was the right thing to do. It _felt_ right.

Maybe, Gaster thought, there was a drop of bravery in him after all.

Then there was a flash of blue - a pressure against his back - the buzz of Sans’s magic -

“No!” Gaster cried, trying to pull away from Sans before he hurt him again. It was too late, however. They were back on solid ground and the impact had once more left Sans in a state that was only moments away from death.

“Why?” Gaster demanded, anger overcoming his concern. “Why Did You Do That?”

“sneaky, g,” Sans weakly laughed. “‘at was… real sneaky.”

“I Was Trying To Help You!” Gaster said. Just as quickly as his temper had flared, it drained into frustration, then grief. “Just Let Me Help You. Please.”

“can’t just… let you fall,” Sans said.

Gaster shook his head. “And I Can’t Let You Do This.” Neither would back down, he knew. Every time he’d turn back time Sans would be there to repeat the action. Neither would let the other die if they could do something about it.

“A Loop,” Gaster realized. “We’re Stuck In A Loop.”

This time is was Sans’s turn to shake his head; he gently inclined his skull, grimacing against the movement. “nah. no loop. i’ll win.” His pained smile took on a hint of smugness. “got more magic... than you.”

Gaster swore under his breath. He was right - of course he was right. Gaster had one, perhaps two good jumps left in him. And every moment that passed meant more magic it would take to make up for it. How much more could Sans teleport?

Enough, Gaster knew. Enough that Sans would outlast him.

“I’m Not Worth It,” Gaster sagged. “This Isn’t Fair. This Isn’t A Good Trade.”

Sans twitched his shoulders, perhaps in a shrug, but his eye lights had gone out. He let out a watery sigh. “dyin’ kinda sucks, g.” His mouth pulled tight into an almost-smile. “but... think i’m gettin’ the hang of it. heh…”

Gaster sunk down even further, his head bowed in defeat. There had to be a way. There had to be something… somehow… someone…

Someone.

There _was_ someone. The idea made Gaster’s soul twist uncomfortably. It was a trump card - a damn good trump card - but it would hurt Sans. Would it be worth it?

Of course it would. It would save his life.

“You Won’t Die Again, Sans,” Gaster said. “Do You Know Why?”

Sans grunted, but otherwise didn’t respond.

“You Have Something To Live For,” Gaster said. His throat felt tight, and he hoped Sans would come to forgive him for this.

“Your Brother,” Gaster said. He began to collect his magic as Sans’s eyes snapped open. “You Have To Live For Papyrus.”

“gaster,” Sans objected, his voice pained. “what’re you-”

“You Made A Promise,” Gaster interrupted, not giving Sans the chance to talk his way out of it. “You Can’t Leave Him Alone - You Didn’t Before. And He Needs You, Sans. Almost As Much As You Need Him.”

“gaster,” Sans pleaded. Were those tears? Gaster looked away. “please, don’t-”

“Goodbye, Sans.”

And then he was falling again.

This time Gaster didn’t let himself hope. He waited, tense, for Sans to reappear. He didn’t know what he would do if it didn’t work. He had no cards left to play.

The seconds that followed were the longest of his life. But they did pass, and Gaster’s fall continued uninterrupted.

It wasn’t until he’d fallen further than he had before that he realized Sans wasn’t coming.

It was with a mix of happiness and fear that Gaster realized he had saved him.

He had won.

Gaster held onto that thought and let it block everything else out. He focused on it with a rabid intensity, a desperation, not willing to let himself think about anything else. Certainly not about the future. Not about what was about to-

Shock first, and then the pain. Excruciating, blistering, mind-numbing, soul-renting pain that ate him away into dust. It scalded and smothered him, boiled up between his bones and filled his skull with nothing but pure, concentrated excruciation that took too long - much too long - to melt his body into dust. And that, even that was nothing compared to the sensation of his soul as it plunged beneath the magma - how? _How could it be worse?_ He’d scream if he had a mouth, plead if he could remember anything but the torture that now had become his entire world-

Instinctively, driven by manic, self-preserving desperation, Gaster’s magic activated and pulled him away. There was a brief, soothing moment in the void - his soul somehow repaired, his body restored - then he was cast back out into reality, only moments before he’d left it. This time Gaster had the presence of mind to cry out before he once more plummeted into the magma, and he felt his body dissolve all over again.

It was worse - worse knowing what it would feel like, and knowing what was about to come.

Again, unasked for, his magic activated and wrenched Gaster from the moment of his death. Again, darkness, then reality. Again, agony and fragmentation. Again, pulled away the moment before his soul could finally shatter - _please_ , just let it shatter -

It didn’t stop. His mind was hardly coherent, all anguish and desperation and, more than anything, a desire for it to _end_. The last scraps of his magic had to burn themselves out sooner or later, but _god_ did he want it to be sooner. _God_ , did he wish for nothing more than oblivion. _God_... did he just want death.

It was justice, some part of him was aware. Justice for the repeated deaths he’d inflicted on the human child. It was fitting. It was hilariously ironic. Perhaps he’d laugh if he weren’t consumed with screams.

But he couldn’t let it go on. He couldn’t take any more of it - he had to make it end. He had to try at least, had to do _something_.

This time, when his magic activated to take him back, Gaster summoned what little willpower he had left and took hold of the wild energy. He yanked on it, commanding it back and away from the laughably brief reprieve it was trying to take him. He slipped into the void as the magic resisted, but Gaster dug his heels in, unwilling to give and be pulled back out into the loop of torture once more.

It was a war with himself. The magic was a part of him as much as he was a part of the magic, and he was grappling with his being - his very soul - in trying to stop what it was meant to do. He couldn’t let himself be pulled back out no more than his magic could let himself stay here.

The void was the space between space, after all. It was a singularity, and it was infinite. It was nondimensional and extradimensional. It was the threshold between spacetimes, the intangible boundary that joined each moment to the next.

It was not a place for souls.

His magic fought to leave to void until it could fight no longer. Finally, in the space between the past and the present, it waned, quivered, and, eventually, went out.

Gaster only let go when he realized there was nothing left to hold. He felt tired, all of a sudden. Relieved, numb, and tired. The pain was over. His strength was gone. The void felt welcoming.

He let it wash through him. He could feel the way his self began to drift. Not up or down or in any cardinal direction, but _apart_. And that, too, was fine with him. He was done being him. Done with… everything. The blackness, the nothingness, was all he wanted now. Let it consume him - let it take him apart. It was better than… something. Something he was forgetting.

The darkness moved in.

Gaster was nowhere.

And nowhen.

And nothing.

 

 

 

**Notes for the Chapter:**

> Thanks for reading.


	19. Beginnings

**Summary for the Chapter:**

> In which this story comes to an end.
> 
> Thank you for reading.

It took Sans eleven months to build the time machine.

He was going to use the one in Gaster’s lab, originally. It was there, just waiting to be used - all Sans had to do was figure out how to get it running. It quickly became apparent, however, that time had other plans.

It didn’t happen all at once.

It was subtle, like water trickling through cupped hands. At first Sans didn’t even notice - he was too busy pouring over Gaster’s notes - but as the days passed the changes became more apparent. Things began to vanish. Small things. A paper here and there, a tool he thought he’d misplaced. It was always when he wasn’t looking, when he wasn’t paying attention, that the items slipped quietly out of existence. Once he realized what was happening he’d quickly and feverently set about copying down any of Gaster’s notes he could get his hands on - before, like their creator, they ceased to exist.

But it wasn’t just physical remnants of Gaster that were slipping away; no, it went much deeper than that.

“how many?” Sans had once asked Alphys. She had noticed first, as Sans had spent the first several weeks after Gaster’s death (disappearance? he still wasn’t sure what to call it) locked away in the old labs, frantically trying to rerecord the Doctor’s research before it was all lost.

“A-almost half,” Alphys had said. “Mostly monsters that worked i-in other departments. A-and more have stopped coming into the Core. Like they just… forgot they work here.”

“maybe they did,” Sans had grimaced. “we should check the records. see if they were all hired by gaster. heh, assuming the records still exist.”

Alphys had nodded, but wrung her hands in worry. “Sans, do you think… do you think we’re going to forget him, too?”

It was just a matter of time.

Even Gaster’s machine had begun to vanish, piece by piece, until one day Sans had opened the door and found the office empty. All evidence of the scientist’s existence wiped clean. Sans had managed to take what notes he could - replicate the blueprints as accurately as possible - but there were gaps. He knew he’d be able to fill them in, but it would take longer working on his own… because, eventually, he _was_ on his own.

Alphys was the last to forget.

It made Sans reevaluate how close she and Gaster might have been. They had always shared secrets, and Sans knew they’d both, to some extent or another, been involved with soul experimentation. They were colleagues, of course, but the way they’d sometimes exchanged a knowing look - the way Alphys’s confidence had recently taken a nosedive - made Sans begin to think there might have been something more between them. He’d always supposed he’d wheedle it out of them one day, but now that wasn’t seeming likely.

When Alphys began to question why Sans was showing up at the Core, confused by his presence, (he had, after all, been Gaster’s apprentice,) he packed up his notes and took everything back to Snowdin. It was quieter, there. Easier to spend time in the workshop behind his house than the eerie, empty labs of the Core. It didn’t feel right, working in a place where a gaping, almost tangible emptiness seemed to fill every room.

Well, not entirely empty.

Sans had seen him once. Gaster. He’d been standing in a doorway, looking at something too distant to be real. Sans had dropped the stack of texts he’d been carrying, stammering out a bewildered “ _gaster?_ ” before the entity in the doorway turned.

It was and wasn’t Gaster. It wasn’t even entirely in this plane of existence. Looking at it was like like trying to see through static, like trying to clutch mist, and Sans mind buzzed with all kinds of primal, frantic alarms.

Like the time at the Extractor, this version of Gaster was all Intent. Sans only caught glimpses of it - confusion, anger, distress, curiosity, (recognition?) - but like before, the impression only lasted a moment before the apparition vanished, and Sans was alone.

Sans had… some theories.

Gaster hadn’t died - not in the conventional sense at least. Sans knew; he’d been there, all those months ago, when time started skipping like a broken record.

It had hit him like a physical blow, strong enough to knock him out of his indecision. (He’d been frozen by Gaster’s words, torn to pieces by conflicting morals, and he’d hesitated for only a few seconds but a few seconds was all it had taken and then - oh god, _oh god he was too late_.) The jumps happened mere moments apart. He couldn’t move, couldn’t breathe, couldn’t do anything but feel reality snapping back again and again, like time had developed a nervous tick. It was impossible to tell how many times it happened, how long it lasted, because it was just a moment, a moment that wouldn’t let itself end, until suddenly, without warning, it _did_. Sans felt the rip in spacetime yawn wide, the void held open - he felt it in his very soul. His magic had been repulsed by the fissure, instincts telling him that this rip in reality was utterly, intrinsically wrong, but the sensation had only lasted for a second. Almost as quickly as it had opened the hole in reality had closed, the time skips had stopped, and Gaster was gone.

He’d become unstuck from spacetime, in all likelihood. It was why Sans had seen him both before and after the event - Gaster was no longer interacting with their world in a linear fashion. He was between reality, resurfacing at random points, and even then only barely able to breach the surface. Sans wondered how old, how unraveled the versions of Gaster he’d encountered really were - if age and sanity were things that could even exist in the void.

 

Sans sighed, looking up at the machine he’d recreated. It was all to go back and fix that one mistake - to do what he should have done in that moment of hesitation. Sans wasn’t sure if he’d ever be able to forgive himself for that. Maybe he wouldn’t have to if he could make sure it had never happened in the first place.

Maybe.

It was a funny thing. He’d always been disappointed in Gaster’s unwillingness to use the machine. He’d understood Gaster’s fear, but wasn’t the risk worth it to do the right thing? If you had the power to fix something, shouldn’t you at least _try_? Yet here Sans was, presented with the same choice, and all he could do was… procrastinate.

He’d finished the machine almost a month ago. Each morning he came down to his lab, pulled back the curtain, powered up the machine and… hesitated. Lord, did he hate himself for hesitating. But he couldn’t help but remember Gaster’s warnings - how this time machine had the same potential to go wrong as the last one had - and he couldn’t help but sympathize with the dilemma Gaster had faced. There was a good chance it would work. A really good chance he’d be able to stop Gaster from falling into the Core. But there was a small chance… a real chance… he would never come back. And this time, it would be Papyrus who'd be left behind.

After another few minutes of staring and thinking, Sans powered down the machine and pulled the curtain back in place. _Maybe tomorrow_ , he thought, taking a shortcut up to his room. There was always tomorrow.

“BROTHER!” Papyrus’s cry rang from downstairs. “ARE YOU AWAKE YET? YOU’RE GOING TO BE LATE AGAIN!”

“yeah, bro,” Sans said, opening the door to his room. “i’m up.”

“OH!” Papyrus said, stepping out of the kitchen to look up at the second landing. “GOOD! I MADE BREAKFAST FOR YOU! WELL, BOTH OF US, BUT I HAVE ALREADY EATEN. MAKE SURE TO HAVE SOME BEFORE YOU LEAVE! A SENTRY MUST STAY ALERT AND WELL FED AT ALL TIMES.”

“i can attest to that last part at least,” Sans chuckled. His brother scowled.

“SANS, YOU SAID YOU WOULD STOP TAKING NAPS AT THE SENTRY STATION!”

“wouldn’t _dream_ of it,” Sans grinned.

Papyrus stomped back to the kitchen. “I’M GOING TO GO TRAIN WITH UNDYNE. YOU BETTER NOT BE LATE TO YOUR SHIFT!”

“ _rest_ _assured_ , paps,” Sans winked, “i won’t be late.”

Papyrus grumbled some more, snatched up his lunch, and left as Sans languidly watched him hurry about. After the door slammed shut Sans dragged himself down the stairs to check out what his brother had prepared. There was some toast and burnt bacon on the table. Sans smiled, grabbing the toast as he slipped on his shoes and jacket. As fun as it was to needle his brother, he did try to get to work on time - most days. Not that there was much to do once he got there, but without the paycheck from the Core he’d needed to help pay for their food and shelter somehow. His brother had suggested the sentry job, and Sans had accepted it out of convenience. It made Papyrus happy.

Sans decided to walk, as a shortcut would just get him nowhere faster. As he crunched through the snow, he thought about the time machine, burnt bacon, and the stone doorway in the forest he’d recently discovered. The latter was a fun mystery, one he’d decided not to ask anyone about so he could try to figure it out on his own. So far as he could tell the door only opened from the inside, and as long as he didn’t know what was on the other side he didn’t want to risk teleporting through to find out. That maintained some of its intrigue, however, which he as in no rush to alleviate. Just another puzzle to mull over while he was on watch.

As always, the day was quiet. Sans thought about the sentry station in Waterfall Undyne had mentioned, and wondered if he should get a second job just to mix things up. Nevermind being in two places at once was as impossible as it was impractical for guard duty, but he didn’t think he would miss much. According to Gaster, it had been years since the last human had fallen into the Underground, and even longer since the one before that. As far as Sans knew, there might never be another human in the Underground.

He thought, maybe, that might be for the best.

Sans didn’t make it until lunch before he grew restless. He tried to stick it out, he really did, but after spending a couple hours sitting at the sentry point, trying not to nod off and doodling equations in the dusting of snow, he’d given up on trying to keep himself entertained. Patrolling the forest was part of sentry duties, Sans reasoned, and his absence at the station certainly wouldn’t be missed. Glancing around the empty trail one last time, he struck off into the woods. Perhaps he’d visit the stone doorway again. That place always got him thinking.

Though the forest was obviously empty, Sans could feel he was being watched. It had been happening for some time, and he’d hope that, if he'd kept ignoring it, it would eventually stop. He was pretty patient, after all. He was good at waiting.

But so was his watcher, it seemed. In fact, it was possible they were more even more patient because they could afford to be; they had time on their side. At least, Sans assumed they were the ones that had been causing the resets.

It had started not long after everyone had forgotten Gaster. The first time it had happened Sans thought it _was_ Gaster - but the time jump was far longer than anything the scientist had been capable of, and of course Gaster was no longer in the picture. Then a couple weeks had passed and it happened again - this time resetting several days. The jump had caused him to lose a significant portion of progress on the time machine, which was annoying - but not as annoying, however, as when the next jump set everything back an entire month. Redoing the lost work was incredibly frustrating. Progress did not come easily when things kept undoing themselves over night. The time jumps had become less frequent after Sans had finished the time machine (almost as if the being responsible for the time jumps had been using them exclusively to screw with Sans,) but they certainly hadn’t stopped. Every once in awhile - sometimes a few days apart, sometimes a few weeks - there would be another hiccup in time, and Sans would be the only one to remember it had ever transpired.

Needless to say, Sans was beginning to grow very tired of timetravel.

“alright,” Sans sighed, stopping in his tracks. “how long is this going to go on for?”

A breezed whispered through the woods, shifting a gentle scattering of snow from the pine. Apart from that, nothing else made a sound.

“you can stop hiding,” Sans spoke again. “why even bother with this game anymore?” He paused for a moment, giving them a chance to reveal themselves. Sans was almost pleased when they didn’t; he quickly summoned two blasters, pointing them back towards a tree a few feet behind him. The weapons whined as they powered up, glowing with ominous light, then-

“Geez! You’re pretty trigger-happy, huh?”

Sans looked at the small, yellow flower that had popped up from a pile of snow. Despite the two blasters pointing at it, the flower seemed all too amused by the situation. Sans had never seen the creature before, but he recognized it from Gaster’s warning.

“flowey.”

“Golly, you already know my name?” the flower tittered. “I guess introductions aren’t necessary then!”

Sans ignored the flower’s dramatics. “you’ve been following me ever since i started working out here. figured if you were going to introduce yourself you would have done so by now.”

“Oh, well,” Flowey smiled, “I just didn’t want to get in the way! You seem _so_ busy.”

Sans snorted, while the flower didn’t even bat an eye. “yeah. busy watching snow fall.” Sans got the distinct feeling that, despite its seemingly sunny demeanor, the flower wasn’t about to give anything to Sans straight. Would jokes loosen the flower’s tongue, or just give it more opportunities to deflect? He had a feeling it was the latter.

“so, bud” he said, opting for the direct approach, “what is it you want with me?”

“Want?” Flowey repeated innocently. “Gosh, I don’t want anything from you. How silly! I was just following you because you’re so very interesting.”

Sans made a noise of disbelief. “really? and what’s so interesting about me?”

“Hm,” Flowey considered. “It’s hard to say! You just carry an intriguing air. Like you’re always up to something.” The Flower’s eyes flashed with curiosity. “ _Are_ you up to something?”

“funny thing, bud,” Sans said slowly, “i was going to ask you the same thing.”

Silence pooled between them as the two monsters stared at each other. Flowey was the first to break it, erupting into a fit a giggles.

“Oh, you are funny!” Flowey laughed. “They did say you’re a comedian.”

“who said that?” Sans asked, seeing his opportunity and attempting to affect a casual tone. “gaster?”

The flower stopped laughing and something flickered over its face. The smile went back up a moment later, but the second of hesitation hadn’t escaped Sans’s notice.

“ _Who?”_ Flowey asked. “That name doesn’t sound familiar to me.”

For once, Sans decided to play the straight man. “he’s an old scientist that used to work at the core. until he fell into it, anyway.” The flower had a fake smile plastered onto its face, which Sans watched carefully as he spoke. “it’s a strange thing, though. see, all the core’s protective shields went down the same night the volcano started acting up. it threatened to melt down the whole core, and everyone in it. gaster fell in trying to save it all. bad luck.”

“Boy,” Flowey agreed when Sans paused, seemingly waiting for a response. “Sounds like really bad luck!”

“yeah,” Sans said. “‘cept I got this theory that it might not have been luck at all. see, the shields couldn’t have just gone down on their own. someone would have had to turn them off - but who would want to do something like that? no one could have any motivation to melt the core down, i thought.” He paused again, watching Flowey, but the monster was unwavering in its look of genuine confusion. “but then i remembered something,” Sans continued. “gaster once told me about these powers he had, and that there was another monster out there with abilities just like his. he said that so long as he was around, the other monster couldn’t use their abilities. so it got me thinking… maybe the shields were taken down not to take out the core, but to take out _gaster_.”

There was a pregnant pause before Flowey next spoke.

“Wow,” the flower said. “That _is_ an interesting theory.”

Sans continued to stare at the flower. “sure is.”

Another pause.

“And did this _Gaster_ person,” Flowey stressed, “ever tell you what their ability was?”

“nope,” Sans said. He wasn’t going to play all his cards at once. “said it’d be hard to demonstrate. what’s it to you?”

Sans wasn’t sure what he had been expecting, but it certainly wasn't a crazed fit of laughter. Flowey had laughed before, but this time was a different. This time the laughter was sincere and soulless. It was a delighted laugh, an unkind laugh, and it chilled Sans down to the bone.

“Oh,” Flowey said between its giggling, “oh, you _are_ interesting. This will be fun! I can’t wait to start playing with you!” The flower tucked its petals in and turned away. 

“hey,” Sans said, trying to stop the flower. It seemed to think their conversation was finished. “hey, wait a sec-”

“Well, toodles!” Before Sans had a chance to finish his thought - or make a point with his blasters - the flower gave a quick twist and popped back into the drift of snow.

“i said wait! i’m not… shit,” Sans muttered. Flowey was already gone. Whatever sort of healthy respect it had held for Gaster did not, apparently, extend to Sans. That was annoying, but Sans suspected he’d be running into the flower again sooner than he’d like. He’d have time to beat a little respect into Flowey - at least enough respect to get it to leave his brother alone.

Sans sighed through his nose and dispersed the blasters. He honestly wasn’t sure what to make of that exchange. The flower remembered Gaster, that much was clear, but he hadn’t been able to get much more out of him than that. If anything, Sans worried he might have given Flowey more information than he’d meant to. He wasn’t sure how much the flower knew, but it was clear it was at least watching Sans to see what he did next. Well, that was probably not the worst thing; maybe he could help keep its attention off of Papyrus. He’d have to learn more about what the flower wanted, first. Its motives still eluded him.

Sans grimaced, turning away from the small mound of snow that marked Flowey’s departure. Best not to spend too much time thinking on it; Sans was good at thinking himself in circles. And he had enough things to think about as it was.

Sans began to walk, his feet guiding him along a well tread path. How had things become so confused? There’d been a time when he’d felt his life had focus. He’d started each day with a goal in mind and finished them knowing he had made some progress. Those were the days he’d felt he had a purpose. Something he wanted to achieve. But now… now the future seemed murky.

The path stopped when it reached the stone doorway, frosted over by Snowdin’s most recent cold snap. Sans looked up at the door, still lost in his thoughts.

There was Gaster to think about, and the time machine of course. Sans would either have to use the machine or think of some other solution to save Gaster. (Assuming, of course, he didn’t eventually forget Gaster like everyone else had.) On top of that, he’d have to find a way to stop - or at least grow accustomed to - Flowey’s time manipulation. Then he had to figure out a way to keep his brother away from Flowey’s attention. Oh, and look into a way to get out of the Underground before they all starved or the volcano erupted. Unless a human appeared first. And then… ugh. Sans didn’t even want to think about what he’d have to do then.

Sans _thumped_ back against the door, leaning into the cold stone. At least this mystery didn’t stress him out. This mystery was an excellent stress reliever, and an even better silent audience for practicing puns. He’d pretty much extinguished his bone and snow related arsenal at this point, and Sans didn’t want his brother thinking that he was going stale.

Sans shoved all his previous thoughts and apprehensions aside and began shuffling through his mental jokebook. There wasn't any puns in particular that he wanted to work on, but then again mindless impulsiveness was sort of the point of this exercise. Absently, he picked a joke at random, then reached up over his shoulder to rap his knuckles against the door.

“knock knock,” Sans said, not expecting anyone to answer.

  
  


 

 

Undertale

  


 

 

**Notes for the Chapter:**

> And... my first real fanfic comes to a close. 
> 
> First of all, thank you to everyone who read this! And special thanks to everyone who left comments and encouraged me to write - you know who you are, and your support really meant the world to me. I probably wouldn't have finished this without you. 
> 
> That said, there was so much more that I wanted to fit into the story but never found room for. I have a dozen more scenes still bouncing around my head, including:  
> \- Sans rediscovering his love of ketchup (EDIT: this has been written, titled "Ambrosia")  
> \- Sans getting his Gaster Blasters  
> \- Gaster's experience when he first arrived in the Underground (could probably be a whole story in and of itself tbh) (EDIT:  
>  "Gazing Abyss")  
> \- Gaster and Alphys background/interactions/soul experiments (EDIT: same as above)  
> \- Sans's encounters with lost-soul Gaster (and his Post-Undertale attempts at trying to get him back)
> 
> If any of that sounds interesting to you guys, let me know! I'll definitely be writing some more Undertale fics in the future, though as to what exactly they will entail is still in the works.
> 
> Again, thank you so much for reading. I wish you all the best.


End file.
